Your Computer Magazine (June 1982)

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JUNE 1982

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LONELY Genie I Microcom-
puter, early eighties, with large
peripheral family but currently
unattached, would like to meet
interesting, attractively pack-
aged software, Genie or Tandy
specification, for programming,
problem solving, entertain-
ment and long-lasting
friendship. Reply in confi-
dence. Box No RS232.

ANSWERING MACHINES

^fke certified.

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Buying your &;st Genie I microcomputer is just the start of a long and enthralling adventure, for it won't
be long befd^tyou will want to expand your system with some of the wide range of peripherals which
make up the complete Genie System.

Firstly there is the The supreme advantage of the Genie I system is

?Vf lfl ft Gl Aft R A V * ts compatibility with the TRS 80, which means

that literally 1000's of pre-recorded programs are
which immediately expands your already available, just waiting to be plugged intc
Genie's capacity to 32K RAM, and your Genie!

up to 48K RAM if required. It can ' , * . it _ ^ .

be connected to 4 disk drives, a The re . cent improvements m the Genie system,

printer, RS232 interface or S100 including Extended Basic, sound unit and

cards. machine language monitor, make it the ideal

Then there is the

Printer,

a compact unit with 80 column, S x

7 matrix print-out, which connects

to your Genie through the

Expander, or via the Parallel

Printer Interface.

^e Disk Drive

gives you greater storage
capacity and full random access
file handling, with the option of
double-density through a
special adapter,
New Dual Disk Drive
now available!

Finally there is Genie's very own

13" Monitor,

a must if you want to let the rest of

the family watch their T.Y in

i peace!

J Available in B & W or green tube.

SPECIAL TECHNICAL GENIE
HOT - LINE ON 0629 4995

for all your technical *dv;ce and service b«ck-jp on any
aspect of the Genie system direct from the experts'

Please send me FREE 16 page colour brochure on the
Genie Computer System. I enclose 25p postage,

Address .

Telephone

C D

-.. ,)/X „ Chesterfield Road.
' (UV Vfl *V Matlock,

A A A Derbyshire DE4 5LE.

*rtAA J iywi/fc<» Telephone: 0629 4995.

Telex: 377482 LowlecG.

J

©§£WvI3

YOUR LETTERS: I O

Beating logic; misadventure; pure artistry.

NEWS: I T"

1 Sharp pocket computer; micro viewdata; and
[ biggcst-ever Computer Fair, - _

COMPUTER CLUB: I /

East London Amateur Computer Club
compares the BBC Model A and B. r\r\

ZX SPECTRUM: Z\J

Tim Hartnell evaluates Sinclair's Spectrum
land pits this colour micro's performance
: against its competition. ^ -

I VIC-20 SOFTWARE: /J\

The latest software for the Vic-20 reviewed by
. Boris Allen, who concludes that the quality
I could be improved. OO

ZX-81 KEYBOARDS: ^O

| Stephen Adams looks at the growing variety of

keyboards for the ZX-81 and decides which

j are the best value for money* aa

FLEXIDISC: OA

A free Othello program on flexidisc. Bill

Bennett shows how this could become a cheap
alternative to software cassettes.

INTERVIEW: %5U

Ron Bissellj of Macronics, talks to Brendon
Gore about a new disc system for the ZX-81.

BBC PROGRAMMING: On/

Features of the BBC Micro not included in the
manual.

VIC-20 MARS: T*U

A space game for the unexpanded Vic* 20 by
Paul Edmond.

BASIC TRANSLATIONS: 40

Tony Edwards continues his series, this
month concentrating on converting BBC Basic
to other dialects.

ATOM UTILITY SET: T"U

David Berry presents a do-it-yourself toolkit
for the Acorn Atom.

ZX-81 MONITOR: OU

A machine-code monitor by John Sylvester
offers features Sinclair missed*

PORTABLE COMPUTER: OO

John Dawson explains how to build your own
portable computer.

RESPONSE FRAME: O I

More answers to your technical queries.

FINGERTIPS: DO

David Pringlc looks at programs and tips for
calculator enthusiasts.

SOFTWARE FILE: D /

Another eight pages of your programs,
including ZX-81, Vic-20, BBC Micro and
others.

COMPETITION CORNER: / v/

Result of the Klingon Death competition and
a further puzzle for a £15 book token. The
Arfon expansion board crossword falls
between pages 18 and 19.

Cover photograph by Stephen Oliver.

Oracle turntable supplied by Ricardo
Firanaffovici.

Editor

TOBY WOLPE

Assistant Editor

BRENDON GORE

Staff Writer
BILL BENNETT

Sub-editors

MEIRION JONES
JOHN LIEBMANN

Editorial Secretary

LYNN COWLING

'Editorial: 01-661 3144

Advertisement Manager
PHILIP KIRBY 01-661 3127

Advertisement Executives

BILL ARDLEY 01-661 3127
PETER RICE 01-661 3127

Midlands Office

DAVID HARVETT 021-356 4838

Northern Office

RON SOUTH ALL 061-872 8861

Publishing Director

CHRIS HIPWELL

Your Computer, Quadrant House, The
Quadrant, Sutton, Surrey SM2 5AS.
Typesetting by In-Step Ltd, London EC1.
Printed by Riverside Press Ltd,
Whitstable, Kent.

Subscriptions: U.K. £8 for 12 issues.
©IPC Business Press Ltd 1982
ISSN 0263-0885

Published by IPC Electrical Electronic Press Ltd, Quadrant
House. The Quadrant, Sutton, Surrey SM2 5A$. Tel: 01-661
3500 Telex/grams: 892084 BIPflESG.

EDITORIAL

The spectrum's arrival on the microcomputing front line will decimate the ranks of
prospective Vic, BBC Micro and Atom users, but will the ZX-81 be its first victim?
Undoubtedly even before their expectant fingers have had a chance to grapple with the
Spectrum's complex shift-key system, many ZX-81 owners will find the prospect of low-
cost colour, sound and memory a lure too strong to resist. But with substantial ZX-81
price reductions in the air — £50 for the basic machine — the 81 will still be in a very
strong position to offer the young or the penurious beginner an ideal point of departure
into computing.

Some of the 180*odd companies which have sprung up to service the ZX-81 with
software, hardware and peripherals have already reported a drop in trade since Sinclair
announced his new colour computer. ZX users are clearly waiting for a sight of the new
micro before deciding to shell out more on expanding their existing systems. But the
attractions of the Spectrum will reach out beyond current micro owners to those who
decided against making the ZX-81 their first machine when they saw its flickering screen
and heard about its capricious loading.

The Vic was aimed at those first-time users. Now one can only speculate on what
Commodore's response will be to Sinclair's latest venture: it will have to be strong if it is
to save the Vic-20 from an ignominious end to a brief career. At £l80-plus for a 2.5K low-
resolution colour computer, the Vic has overnight became a radically less attractive
proposition when compared with the £175 needed to secure a 48K high-resolution
Spectrum. Drastic price cuts seem the only answer. Commodore's £100 Ultimax might
have had some say in the matter, if it had not been shelved for the immediate future.

In any case the Spectrum will not have it all its own way. The BBC Micro, despite its
higher price, still has features that Sinclair's colour micro cannot rival — a real keyboard,
sound synthesiser and composite video, for example. Furthermore the Electron, Acorn's
still-secret weapon, could present the Spectrum with some very tough competition.

Perhaps the last variable in the micromarket equation is Sinclair's Microdrive. Coupled
with the power of the Spectrum, the appeal of 100K mass storage for £50 may add up to a
renewed period of the Sinclair domination which started with the announcement of the
ZX-80 in January 1980.

The projected new price for the ZX-81 is £80 with the 16K RAM pack. That should be
enough to ensure steady sales in the U.K., and continued success worldwide. At the same
time, the cost of the ZX printer has discreetly risen to about £70. Sinclair has made it clear
that he will not stop ZX-81 production. In any case, unlike programs loaded into a wobbly-
RAM pack, the 350,000 ZX-81s already sold will not just vanish into thin air.

YOUR COMPUTER, MAY 1382 3

nil

electronics

48 JUNCTION ROAD, ARCHWAY LONDON N19 5RD 100 yds FROM ARCHWAY STATION & 9 BUS ROUTES
TELEPHONE: 01-263 9493/01-263 9495 TELEX: 22568.

YOUR SOUNDEST CONNECTION IN THE WORLD OF COMPUTERS

VIC 20

* 24 Colours, 8 for Characters, 8 for Border,

16 for screen mixed as you wish.

*3 tone Generator for sound.

'Uses Pet Basic 'Plugs into T.V.

'Memory expandable to 32K

'VIC complete with

T.V. Modulator and

Power Supply

ONLY £165.00

VIC Cassette Deck
ONLY £38.00

Available soon
VIC Dot Matrix Printer
80 Column, 30 CPS,
Tractor Feed
ONLY £199.95

■UK101

tfo,

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UK101 Kit inc8K memory £125
Ready Built inc 8K memory £175

Complete in case £199

4K Expansion 8x21 14 £10

Parallel Printer Interface £24.50
Cases £19.95

Chromasonics Sound Kit £24.50
Colour Kit £69.95

NEW NEW NEW

32K Dynamic Memory Board
only £89.95

P.I.O. and Eprom Programmer Kit
only £24.50

APPLE II PLUS

AUTOSTART "EUROPLUS"
48K Apple Computer 649.00
Disc Drive with Controller

349.00
Disc Drive without Controller

299.00

Colour Card 69.00

Silentype Printer 199.00

Graphics Tablet 425.00

V Modulator 14.00/

A range of Apple
Accessories and
Software are
available

-PET

4016 16K RAM 445.00

403232KRAM 569.00

8032 32K RAM 755.00

8096 96K RAM 960.00

4040 Disk Drive 585.00
8050 Disk Drive 755.00
4022 Printer 80 Col 357.00
8024 Printer 132 Col 975.00
8026 Printer/Typewriter

835.00
8027 Daisy Wheel 735.00
A range of Pet
Accessories and
Software are available

PRINTERS-

*

INTERFACES AND CABLES
FOR APPLE!/, PET, TRS80.
RS232, UK101, SHARP
SUPERBOARD - ALL
AVAILABLE.

EPSON MX80 FT/1 £399

Dual single sheet friction and
tractor feed. 9 wire head, true
descenders
EPSON-MX80 FT/2 £440

An FT/1 with high resolution
graphics.

SEIKOSHAGP80A £199

Dot matrix 5 x 7, 80 columns, 30
cps graphics, double width
characters.

JUST PHONE FOR FURTHER DETAILS

EPSON MX80 £359

Dot-matrix printer with Pet
graphics interface. Centronics
parallel and senai. Pet and
Apple compatible. True bidirec-
tional, 80 cps.

EP80 MX82 £389

As MX80 plus high Resolution
Graphics

-VIDEO GENIE*

£299eg3003

Utilises Z80, 12K level II Basic, In-
tegral Cassette Deck, UHF O/P, 16K
RAM, all TRS80 features. Simply
plugs into monitor or UHF TV. With
V.U. Meter.

PARALLEL PRINTER INTERFACE INC CABLE £38.00

CHROMASONICS PROGRAMMABLE SOUND KIT £24.50

SOUND KIT (FITTING EXTRA) £8.20

LOWER CASE KIT (FITTING EXTRA) £29.80

COLOUR KIT (FITTING EXTRA) £36.00

EXPANSION BOX INC 16K RAM £199

16K/32K RAM BOARD £94/ £129

NEWGENIE II NOW AVAILABLE £310

MONITORS

9" Green Screen £99.00

12" Green Screen £125.00

12" BMC Green Screen £159.00

HITACHI PROFESSIONAL
9" £99.95

12" £149.00

■TANTEL-

PRESTELBYTANTEL

COMMUNICATIONS AT YOUR FINGERTIPS
FOR BUSINESS & HOME. UP TO DATE INFO

180,000 pages of information on Travel, News,
Investment, Holidays, Hotels Etc., Etc.

£159

TANTEL IS POST OFFICE APPROVED. SEND FOR DETAILS.
DEMONSTRATION AVAILABLE AT OUR SHOWROOM.

lAJtCUYXAJttl

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ALL ITEMS CARRY A ONE YEAR GUARANTEE

Please add VAT 15% to all prices. Postage on computers, printers and cassette decks charged at cost, all
other items P&P 30. Place your order using your Access or Barclaycard f Min. tel. order £10). Export enquiries
welcome. Official orders welcome.

4 YOUR COMPUTER, JUNE 1982

r v

cnwvtaSATio***. 3*w-$h

When adult
education becomes

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MAIN DEALERS FOR

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B.B.C. ~Af AM

AND SOFTWARE SPECIALISTS

Complete with BASIC
language cartridge and

manual
Available whilst stocks last!

plus AIAM410
CASSETTE RECORDER
NOW ONLY £45

It's here at last!
B.B.C Microcomputer
Games Pack 1

Suitable for BBC models A & B

GAMES PACK INCLUDES

STAR WARS - BLACKJACK

ALIEN INVASION - SIMON - FORTUNE

Phone for details ACORN ATOM Packages

for further information send large S.A.E.

Computers
for All

72 NORTH STREET,

ROMFORD, ESSEX.

TEL 0708 60725

BARCUYCARDj

YOUR COMPUTER, JUNE 1982 5

flNGLD AMERICAN SDFTUJflHE CD

BBC - TRS-80 - ATARI - PET - APPLE - VIC - ZX81

We know what it is like out there, because that's where we came from. Before we decided to become software
entrepreneurs, we were just like you enthusiasts searching through magazines for the ideal mail order software
source. What we hoped to find was a single entity that offered an ultra-wide selection for our micro-computer.
That pre-selected only the best of many similar sounding programs that reached the market every month. That
could give us personal assistance with the purchase-decision process, and that stood behind its products. When
we couldn't find it wedecided to become it. So ANGLO-AMERICAN SOFTWARE CO WAS BORN.

Please state clearly the program (s) you require. Include your name, address & machine type + memory size.
Prices include VA T, postage & packing.

QILTYC Q QN

What would it be like to be an oil
producer. Find out with this action
packed simulation as you try to
become an oil tycoon. Explore for
new wells get reports, name your
own price for oil - but don't get too
greedy or beware. The game involves
strategy and chance. You could end
up as one of the wealthiest men in
the country or the bankrupt victim
of too many oil spills. You will
find OIL TYCOON both challenging
and exciting.

PRICE £9.95
CASSETTE

DUNGEON OF DEATH

Your quest is to search for the Holy
Grail where you descend through 12
levels, find the Holy Grail and return
to the surface. The Grail is guarded
by SMAUG the most fearsome
monster of all and ten lesser breeds.
You can only survive by using all the
powers at your command. You can
cast magic spells, drink potions that
may or may not help you find items
to help you fight the monsters. Step
softly in the darkness. Treasure or
sudden death is only a footfall away
in the DUNGEON OF DEATH.

PRICE £10.75
CASSETTE

MASTER DIRECTORY
Wasn't it yesterday you threw the
cat into the washing machine because
you couldn't find where you had put
the last Adventure game you had
saved or was it that you gave your
mother in law the leftover curry
because your three year old had
mixed up all your data disks and now
you don't know which one is which.
Well cheer up MASTER
DIRECTORY is here. The M.D. is a
storage program that reads the files
on your disks, stores the name,
extension and even records the free
space on each disk. All you do is
number your disks. You can use it
alphabetically or search for name and
ext search for free space. Store 5000
files or 320 disks.
Requires one disk drive.

PRICE £21 .00
DISK

THE FLYING CIRCUS

Is a package covering biplane to

modern day planes. These seven

programs offer you the daring

realism of flight.

LAIR FLIGHT

2.NIGHTFLIGHT

3, AIRMAIL PILOT

4. MOUNTAIN PILOT

5. 0'HARE (air traffic controller)

6. APPROACH RADAR

7. JET FIGHTER PILOT

A great combined flying package.
Try to master the lot.

PRICE £25.00
DISK

AIRFlinHTSIMIllATlON
Instrument takeoffs and landings are
no picnic ask any pilot. This com-
puter simulation is sure to keep you
on the edge of your seat. You begin
with a full tank of fuel and a flight

plan to learn simple take-offs
and landings. Pay attention to
your instrument panel too steep
a bank and your air speed -will
drop like a stone. . . so will your
plane. It's about as close to the
real thing as you can get this
side of the runway. Fun for all
the family when you learn to do
acrobatic manouevres.
PRICE £9.95
CASSETTE

SANTA PARAVIA & FIUMACCIO
Fancy being a MRS THATCHER
well with this program you will come
as near to it as you will ever be.
Perhaps I should acquaint you with
the domain. It is not a wealthy Area
but riches and gl ory are there for the
aware. You will have to worry about
the serfs requesting more grain if
they don't get it they may flee.
There is the weather as well if it is
good so will the crops be. You may
find you have to increase the tax.
You may also wish to build a new
palace to measure your progress the
official cartographer will draw you a
map so as to see how to plan your
strategy. A very entertaining game.

PRICE £10.50
CASSETTE
PRICE £1425
DISK

SEND 75p FOR FULL
CATALOGUE

Refundable against purchase

Dealer Enquiries Welcome

ANGLO AMERICAN SOFTWARE CO.

138a Stratford Road
Sparkhill

BIRMINGHAM B11 1AG
021 771 2995

6 YOUR COMPUTER, JUNE 1982

PES

24 hour ansaphone

*■ PROGRAM OF THE MONTH <*

SPACE SHUTTLE
Save £4.50

5.3 million pounds of thrust sent the space shuttle
COLUMBIA into orbit. Now on-board computers will
help to bring her safely and gracefully back to earth.
SPACE SHUTTLE puts you in the command pilot's
chair of the first reusable space vehicle and until com-
mercial flight becomes available this is the closest you
will.get. We feel this is one of our best programs.
PRICE £17.00 Special offer price of £12.50 CASSETTE.

NEW!

Justreh

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FAST ACTION...

KILL THE

ATTACKING CREATURES

lilEGAL

MEGALEGS. .more than just another
computer game
...it's exciting
...ifs challenging

...it's a spectacular arcade game with a
new dimension ot excitement and...
...it's destined to be one of 82s most
fascinating and most demanded fun
games* Collect points by killing off the
attacking creatures. As your skill improves,
the attackers speed increases.
Will you survive?

Joystick required.

Available on disk or cassette... only $34.95.

/A,

for

ATARr

[400 and 800
\C0MPUTERSi

16K

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£§§25

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i Order direct from:

ANGLO AMERICAN SOFTWARE CO
138 STRATFORD ROAD

SPARKHILL

BIRMINGHAM B11 1AG

021 771 2995

DEALER ENQUIRIES WELCOME

./

s*\

A I AMI mi I A I AIM m II Aitft A0O .1

YOUR COMPUTER, JUNE 1982 7

Micr o Gen

QUALITY PRODUCTS

ZX81 A/D CONVERTER BOARD

This 4 channel analogue to digital converter originally
developed for joystick control, can be used for such
applications as measurement of voltage, temperature, light
intensity etc.

The board fits in between the RAM pack and the ZX81 . (No
skill is required to make this connection, and it actually
improves the stability of the RAM pack).
Price now only £18.50,

JOYSTICKS FOR THE ZX81 only £9.60 each

*The most exciting add-on ever for the ZX81, free

yourself of that dead, unresponsibe keyboard,

*1 or 2 joysticks may be connected via our A/D board.

*Turn$ your ZX81 into a true programmable games

machine,

*Extends the capability of the ZX81 , imagine the

tremendous variety of games and applications that now

become possible.

* Details supplied on how to use the joysticks in your

own programmes.

Please note that you cannot connect conventional analogue
joysticks directly to the digital input ports found on most
I/O boards, an A/D converter such as ours is required.

A free copy of ZX AMAZE plus any one of the games listed
below when ordering a joystick and an A/D board.

PROGRAMS AVAILABLE

ZX SPACE INVADERS.

You've tried the rest, now try the
BEST. This program has many features including an ever
increasing rate of play (they'll get you in the end).

only £3,95

ZX BREAKOUT.

Quite simply the best breakout on the
market. Features seven bat angles, (you won't find this
one easy). only £3.95

ZX NEW YORK.

[A very addictive arcade game.
Bomb and shoot your way out of trouble, otherwise you
are doomed to crash. Generates a different pattern, for a
different game each time you play. On the reverse of the
cassette is ZX REFLEX, find out how fast you really are.
now only £3.95

ZX CHESS.

__ The original and still the best. * Graphic
display of chessboard * 6 levels of play, * Displays record of
your moves and the computers. * Board can be set up to any

position. Has ability to change sides or level in mid -game.
* PLUS * CHESS CLOCK on reverse side, records time
* Resetable function, *

taken by each player,
entry.

Single key

NOW ONLY £6.50

IORfiWaD* fiia«otr^^^rwigWP nn cv;s you to sntsr and
run your own machine code. Relocates to top of memory
to allow you to load other programs and find out how they
work. Block move. Byte search. Load display and alter all
CPU registers* Window on memory facility, uses standard
mnemonics, an absolute necessity if learning machine code

Only £3.95

All our games are written in machine code, and can be used
with joysticks or keyboard, (except chess, keyboard only).
Supplied on cassette with library case.

To allow you to prove to yourself that our products are
second to none, MICRO GEN offers the following terms to
our customers.

14 DAYS FREE APPROVAL ON ALL PRODUCTS
All money will be refunded if goods are returned in good
condition within 14 days of despatch.
If you write a program which is exceptional, please submit
it to us. We will offer a royalty if it is suitable.

Cheques + POs Payable to MICROGEN 24. Agar Cres,
Bracknell, Berks.

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Centre, WELWYN GARDEN CITY Rumbelows WETHERBY Bits
& Pieces WOLVERHAMPTON Dixons WOODFORD Rumbelows

:

Texas Instruments

With the Home Computer fromTexas Instruments,
you can converse in the five major languages:
BASIC, PASCAL, TI-LOGO, ASSEMBLER
and it speaks English!

When you compare the TI-99/4A Home
Computer to its competition, you'll find it is a
truly remarkable machine. For a start, it enables
you to use the most important programming
languages. Something that is difficult to find on
other comparable computers. What's more, it
has a large 16 K Byte RAM memory capacity,
expandable to 48 K Byte. With the addition of
certain peripherals and a Solid State Software^
Module a total combined RAM/ROM capacity
of 110 K Bytes is available. The TI-99/4A Home
Computer plugs into an ordinary TV set and
can be expanded into a complete computing
system with the addition of peripherals such as
two ordinary domestic cassette recorders, remote
control units, disk memory drives, speech
synthesiser, and thermal printer. Via an RS 232
interface option* other peripherals such as
communication modems, impact printers and

plotters can be attached. With it's high resolu-
tion graphics with 32 characters over 24 lines in
16 colours (256 x 192 dots), three tones in five
octaves plus noise, and BASIC as standard
equipment and options such as other program-
ming languages - UCSD-P ASCAL, TI-LOGO
and ASSEMBLER- and speech synthesis, you'll
find that the TI-99/4A Home Computer more
than compares with competition. Especially
when the starting price is £340 or less. When
you want to solve problems there arc over 600
software programs available worldwide -
including more than 40 on easy-to-use Solid
State Software* Modules.

After all, from the inventors of the micro-
processor, integrated circuit and microcomputer,
it's only natural to expect high technology at a
realistic price. f \ o

The T1-99/4A Home
Computer: another way we're
helping you do better.

We'll help you do better

Texas Instruments

YOUR COMPUTER, JUNE 1982 9

- AUTOMATIC

- TAPE CONTROL

The logical extension for £ e „
the Sinclair ZX8I giving v $5

data retrieval & word processing

EXTENSION

BOARD FOR NORMAL

SINCLAIR ACCESSORIES

BUSINESS, EDUCATION & FUN

The ZX99 Tape Control system is a sophisticated extension to
the Sinclair ZX81 Microcomputer, providing remarkable
additional capabilities, which allow both the beginner and
expert access to a professional computing system without the
expected expense.

*DATA PROCESSING

The ZX99 gives you full software control of up to four tape
decks (two for loading and two for saving) allowing 'mixing' of
data files to update and modify them. This is achieved by using
the remote sockets of the tape decks to control their motors as
commanded by a program.

* PRINTER INTERFACE

The ZX99 has a RS232C interface allowing you direct
connection with any such serial printer using the industry
standard ASC1 1 character code (you can now print on plain
paper in upper and lower case and up to 132 characters
per line.)

* MANY SPECIAL FEATURES

There are so many different features that it is difficult to list
them all:
For example:

AUTOMATIC TAPE TO TAPE COPY: You can copy any

data file regardless of your memory capacity {a C90 has

approx 200 K bytes on it) as it is loaded through the Sinclair

block by block.

TAPE BLOCK SKIP without destroying the contents of

memory.

DIAGNOSTIC INFORMATION to assist in achieving the best

recording settings.

The ZX99 contains its own 2K ROM which acts as an extension
to the firmware already resident in your ZX8VS own ROM. The
ZX99 f s ROM contains the tape operating system, whose
functions are accessed via Basic USR function calls. Each
function has an entry address which must be quoted after the
USR keyword. All of the functions can be used in program
statements, or in immediate commands (i.e. both statements
with line numbers and commands without them).

COMPREHENSIVE USER MANUAL INCLUDED IN PRICE

REAR

E312

TAPE DRIVE
(ALL REQUIRED FEATURES)

COMPUTER CASSETTES

QTY

PRICE

TOTAL

ITEM

QTY

PRICE

P&P

TOTAL

C5

Z5p

ZX99 Automatic Tope
Controller +
Super Software

£
5995

£
295

CIO

37p

CI2

38p

E312 Gmette Tope Drive

24-00

100

CIS

39p

Cheque PO payable k> Srorkcose l?d

K9 flU °*

C20

41p

C25

43p

1 *" ■ ' WBmJ Charge my Access/ Visa card no:

C30

44p

i

C15 LeodeHess

£100

sirtNen

Addmm£150orlO%PS.P

ORDER FORM TO:

data-a//ette.

Dept=YC2

44 Shroton Street.

London NW1 6UO Tel: 01-258 0409

Telephone enquiries welcome

NAME

A0DRESS .

10 YOUR COMPUTER, JUNE 1982

ZX81 HEWSON CONSULTANTS ZX81

HINTS ft TIPS for the ZX81 £4.25

by ANDREW HEWSON

"Good vahj* and quit* fa$c*ndW9 , . . a very inexpensive way of acquiring months oi
programming experience" Your Computer Nov 1981

"Excellent . . . very good value f of money" SYNC

80 pages exp-'5inin9 how to squeeze a computing quad out of a Sinclair pint pot.
Saving Space — vital reading for all 2X81 users.

Understanding the Display File - using the display file as merwv, clearing a part of
the display, using tockens in PRINT statements. Covnerting ZX80 programs -
explaining simply but comprehensive^ how to convert the hundreds of published ZX80
programs. Chaining programs — revealing techniques for passing data between
programs, calling subroutines from cassette and establishing da la tiles. Machine Code
Programs — all you want to know about 280 machine language Explaining how to
write, load, edit and save machine code and how to debug your routines. Routines and
programs are scattered liberally throughout the text and the final chapter consists of 12
useful, interesting and entertaining programs such as LINE RENUMBER, BOUNCER.
SHOOT, STATISTICS, etc. ^_

16K RAM £37.50

A top quality add-on memory, simply plugs into

the back of your Sinclair computer. Can be used

in conjunction with the ZX printer. Neatly

packaged in a black plastic shell to match your

ZX$k Supplied with one year's guarantee.

ZX81 "SPECIAL OFFER" FREE COPY OF OUR

SUPER SPACE INTRUDERS' CASSETTE with

ANY order for the 16K RAM received by 23.5.82.

One copy per customer,

64K MEMORY £79.00

Developed by Memotech this amaiing 64K RAM needs NO extra power supply.

Simply pHigs neatly and firmly into the rear port of your 2X81 . Can be used with the

ZX printer and other add-on hardware. Just look at these features , . .

*$M6K can be switched in and Out in 4K blocks to leave space for memory mapping i.

♦ J2-16K can be protected against overwriting during loading from cassette.

♦directly addressable a^d user transparrent.

*up to 15K of basic program.

♦32K or more of variable area.

16K SOFTWARE

SPACE INTRUDERS £5.96
Not to be missed. AH action display. 40
alien ships »n each squadron, Automatic
option — the machine plays itserf.
Squadron after squadron of aliens attack
your position. Three laser guns. Full
score display. Written in machine code
for super fast fun

*J

PROGRAMMERS TOOLKIT £6.50
Are you writing your own programs for your 2X81 ? Then use Our TOOLKIT to do the
donkey work. Copy into RAM before you start work and then you will have it at your
fingertips. Comprehensive LIKE RENUMBER including GOSU8S and GOTOS; LOAD,
EDIT and RUN machine code programs; INSPECT the 2X91 system routines; COPY
them into RAM and PATCH and /or EXTEND them; FIND a given piece of BASIC code
and replace all occurrences of it; move blocks of Basic lines with EDIT.

LANGUAGE DICTIONARY £3-75

Now you can construct your own English /French, English Anything dictionary with our
LANGUAGE DICTIONARY. UPDATE the entries. SEARCH for a word, CREATE a new
dictionary and save it on tape.

1K SOFTWARE

MINI INTRUDERS for the 1K machine £3.95

An incredibly fast moving game, dodge left and right to avoid failing missiles. Fire Sarvo
after Salvo at the attacking aHen squadron, more aliens join the squadron all the time-
Count how many later bases you lose before you have cut them down.

PLANET LANDER £3.75

Four programs:

\) Planet Lander; hj Space Docking; fii) Stopwatch, iv) Clock.
STATISTICS £3.7S
Three programs:

11) (I J Statistics; prints the current mean and standard deviation after each value is
entered. (II) Regression; prints the current mean and standard deviation of the y values,
the x values and the intercept and slope of the regression line, ill I) Trend; prints the
current mean and standard deviation of the y values; the x values and the intercept and
slope of the trend tine,

12} Chi square test calculates the value of the cN square statistic fo* comparing
observed and expected values.

(3) Graph pk)t; plots a graph of data entered from the keyboard.
Special offer
Cheque With Order Or quote aCCeSS number tO: Mini Intruders and Planet landci £5.00- Offer closes 23.5.82.

HEWSON CONSULTANTS, Dept. YC, 7 Grahame Close, Blewbury, Oxon OX11 9EQ. Tel: (0235) 850075

280 OP CODES a. 45

A must for the beginner and the experienced programmer alike. This handy ready
reckon lists all the 600 plus 280 machine code instructions ta decimal and hexadecimal
with their mnemonics. Each Op Code is succinctly explained and cross* referenced.
Supp icd in a protective transparent wallet for easy reference and durability.

The ultimate

SINCLAIR ZX 81 (16K)

DATABASE FILING SYSTEM

by DALE HUBBARD

Fed up with boring games — make your ZX81 work for you!
The one you've been waiting for!!

Cassette based

Clear "menu" operation

Facilities include sort, search, list, delete, change, total numeric field, save and load file, line print, etc.

Complete with demonstration file and full instruction /application leaflet.

Requires 16K Ram pack.

Applications: Recipe file

Stamp/coin collections

Inventory Control

Employee Data

Record Collections

Magazine article catalogue

May be used for any application where fast access is required to stored information

Access accepted

Send cheque or P.O. or credit card number to:

GEMINI MARKETING LTD.

Quay House, Quay Road, Newton Abbot, Devon TQ12 2BU

OR telephone us with your credit card order
on Newton Abbot (0626) 62869

DESPATCH BY RETURN

ONLY

£5.95 FULLY INCLUSIVE!

w

e<

\«

&

YOUR COMPUTER, JUNE 1982 11

SHARP MZ80K (48K ram)

^SUPAVALUE

fi&

CBM VIC

NASCOM

KITS

NivcennT,w«h

NAS^YSlkitfiO

C1 11 SO

NlKOm 2, no «i«r RAM

£202.50

BOARD LEVCL

N'*Kom*,w*h

NASSYSHewPJO

£12600

NiKom 2. iy> u*er RAM

C23&SO

CASED SYSTEMS

Nucom 3, no u**f RAM

C33MC

6K«wRAM

£16.00

V6Kvi^rRAM

mso

32Kow<RAH

mojso

-*e*U**rRAM

C117,00

power sum.Y

Kit form

C2*.2S

MEMORY CARDS

RAM. & fr.*mory ard

with 16K RAM - hit

£7100

RAM 3 rr-tmory card

w.lh 16K RAM bo*rd

£90.00

AddUkXMMOXftAM

£13.50

AtfdJtk^jl 31K RAM

£27.00

I/O BOARDS

OO board* foOxPJO,

ixCTC.TxUART

W«x«0

£40,50

PJ0for*bov*l/O

£10.K>

CTCfofibovcI/O

£12.60

UART for above I/O

£14.40

DISC SYSTEMS

Niicom vrvjtt d»*e d>l*e

i3S0KBl.nd.FDC care

£423.00

\*ucc*yi dual d«K

drtv« (JSOKB eKh>

i*d,FDCc*rd

£61650

MAS DOS dt»c op sytum

£40. £0

SOFTWARE

MAS-SYSTROM

NAS-SYSJEPROM

ZEAP2.1forNAS

SYSift4xEPROM

ZEAPlHorNAS

SYS oiv op*

$< i- irow'l

b*^c m ROM

£10.80

moo

£26.30
£22.50
£18.00

800 Computer
400 Computer
border
OxkOrtvt
16KRAM
[OyttJ«i« {pair I
84*nk Dfckertw (S>
Awei-nbier E - w -
So4<«lftv«jen(RO«J
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tfiritafcon to
Programming (t)
ln%1tatkM> to
faframmtngO)
Tooth Typist

C0ftvtfMt(0<"4J f r*T<h
Cony tnitiom} German
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o

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z

SHARP PCI 211

|E3 o £3 © CDQ B S CSS 1 *"

v:C 20

viCC«*«ttUft»t
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VIC SOFTWARE

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tatro to PASCAL

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Prof*am xh« Z-BO
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6S02 Application* Book
Ad-iftted BASIC
Apple II VuSt Guide
?oi - BASIC

BASIC Bu*ne*i Software
BASIC Computer Garnet
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tOtoomt)

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Getting acquxnted w»th
your Acom Atom
ImcjRt BASIC
M<rotVoJ0
Bet>^.'>er■* Book
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B'-arJtCU
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for 10

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4 ^ 161 Bramiey Ro*d ( Oikwood, London N14 4XA
Tekphone: 01-363 8060.

OprnM = --Si;.«-5.3C.

X?

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TURN 'LISTINGS' I WTO
DYNAMIC ZX GRAPHIC PROGRAMS

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Within hours you'll discover all sorts of ways to change "words" into computer "pictures"

and produce realty dynamic programs!

You can do it easily with the he ! p of a PRINT 'N' PLOTTER

JOTTER and FILM.

The JOTTER is a 1 00 page Graphics Pad designed for the

ZX81/80. Every page has a PRINT and PLOT grid showing

the screen locations. It tells you any part of the screen in

seconds, and gives you a 'sketchpad' to produce incredible

graphics for games, business programs, information

panels, tabulations - everything the normal 'listing' lacks!

PRINT 'N' PLOTTER FILM is used with the JOTTER and is a man, transparent, film

version with identically-sized grids. Use it to co-ordinate PRINT or PLOT, or use it to 'copy'

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dynamic programs, whether you're convening existing listings or writing an original.

Ask for them at your local Comp Shop, or send today for mail order.

GOODnEWS

■*■ FOR .&.

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(MIERS

JSBfcr

If you do not wish to use this coupon write, stating your requirements,
To: Print V Plotter Products (YC319 Borough High Street, London SE1 9SE.

□ Please send me . . . . JOTTERS <§> £3.50 □ Please send me . . . . FILMS @ £2.25

a Please send me ... . MANUALS @ £1.00 (£1.50 if ordered without JOTTER or FILM)

D Remittance enclosed a Bil my Access/Visa No:

2 hole*
punched

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Numbered
PLOT Grid.

Address

YC3

100 Sheets. Size A4.
Board backing.

Noir Ofdtrt in uuilfy potted within 4$ hours of rtitipt tf yoo roquif 1 1ft Ciits pott pfeatt add SOp to order.

:1

AvtitebJ* at • Sutfar Mic«» Shop 374a Sfr eat lum M«h Ro* London SW16 « Oenny't Booktt«trs2Canngs«nSt. London EC! * Mlerowar* 131 Metion Rd. Letcattor

12 YOUR COMPUTER, JUNE 1982

YOUR LETTERS

1

UNBEATABLE LOSER

fbny Poultcr claims his noughts
and crosses program, in
February's Your Computer, is un-
beatable. This is only true if you
play logically. If you play X and
arrive at this position:
3
5x7
9 x B
by playing 6, then A, your logical
move is 3 to block the computer's
winning line> but play 9 instead and
the computer ignores the chance to
win and tries to block you by playing
B> leaving you to win with 3.

Paul Blythe's Brahma in April's
Your Computer works on the ZX-81
IK but only by changing line 140 to:

LETA(b,E-1»»A(C,B)
to stop rings disappearing. Also, you
do not need extra memory to have
more rings. By replacing all
numbers in with Code"Chr$n"
except for 0, 1 and 3 which can
become Sin Pi, Sgn Pi and Int Pi and
renumbering lines 70, 75, 80 as 61,
62 and 63 you can have up to nine
rings with room to make an illegal
move or two.

Jack Betteridge's Prime Numbers
program in April's Your Computer
has a misprint in line 200 which
should be:

IF P-0 THEN GOTO 250
Line 1 10 can be changed to:

IF CO Y THEN GOTO 140
It also needs some changes to run on
the ZX-81:

150 IF A = INT (A/2) # 2

THEN LET A=A + T
160 FORY = ATOBSTEP2
180 LET R - INT (Y/Q)
Delete 250
To stop 1 being reprinted when
A- 1, add:

145 IF A=l THEN LET A = 2
Although mentioned in the Sinclair
manual on page 74, 1 have not seen a
Software File program using Goto as
a conditional expression. One could
be used in B T Jeeves's Satellite
Plot, April, making the following
changes: Delete lines 50, 60, 70,
100.
55 CLS

65 GOTO (10 AND A<>1 AND
AO2)*l75AN0 A = 1) +
(105 AND A-2)

K Feary,

Wendover,

Buckinghamshire.

PORT POINTS

•A^ith reference to Stephen Adams*
f^frecem review of ZX-81 Ports,
we would like to clarify the
following points concerning our
16K RAM and LO board. Our board
is usually supplied complete with
0.5A power unit for £53, but is avail-
able without for users who already
have a suitable unit. The board will
not work without a separate power-
supply unit as its + 5V and -5V are
derived on board from the 12V. Data
sheets for the 8255 cost 50p with the
board or 60p separately. General

data will be sent on receipt of a
stamped, addressed envelope.

The edge connector is included in
the price, although wx can supply it
separately for £3.20. The kit is not
available, but we can supply the bare
printed-circuit board with
constructional data for £10.75.

We recommend that the board be
cased not because of hazard to the
user, but to protect the board from
accidental short-circuit or
mechanical damage.

K Reeman,

Ground Control,

Hullbridge,

Essex.

MISADVENTURE

rhere are a few minor errors in my
Adventure program published in
April. In lines 2904 and 3110 the
number 10 should be the variable
IO, the index of the object entry.
Second, I have now amended lines
2420 and 2430 which should be as
follows:

2420 IF X$0"INIT"

THEN GOSUB 6700
2430 IF X$<>"INIT"

THEN GOTO 1000
2440 GOTO 70
This is necessary because the ZX-81
does not Save the Gosub stack. With
this amendment a Saved game will
automatically recommence after
Loading.

Graham Thomson,

Northzvich,

Cheshire,

STRING LENGTH

jjraham Thomson's Adventure, in
^r April, is an example of the
intellectual satisfactions the ZX-81
can offer. His method of storing data
in a single long string is a fascinating
technique.

However, after spending much
time in keying in Thomson's pro-
gram and debugging my keying
errors, I came to the conclusion that
it, rather painfully, reinvents the
wheel. In indexing a single long
string one is almost writing a fresh
ROM when the Sinclair ROM with
its multi-dimensioning of strings
already supplies a ready-made and
clear index to vast numbers of
strings.

My own attempt to write a Dr
W^ho adventure, anticipating a visit
from my grandson, employs a four-
dimensional string, i.e., P$
(X»Y,X>20), the initialisation being

10 DIM P$(2,3,5,20)
InkeyS is used to change the values
of X, Y and Z. Thus a Go North
instruction, press key N, is prog-
rammed to add 1 to % depressing
key S subtracts 1. East or westwards
moves are achieved by moving across
the third dimension, by changing the
value of Y.

Journeying into outer space or a
new time zone is achieved after dis-
covering Tardis, by using the U key
to alter the value of X when a whole

new hierarchy of places arc opened
up to north, south, east or west
movements.

Object discovery is very simple.
Arrival at a place for the first time
causes the program to Gosub when
the object and its score are digested,
the object being put into an OS string
at a predetermined place:

LET 0$(23 TO 28) = "GOLD:"

Objects held are primed to the
screen constantly, simply by calling
a print of 0$, without dimension. No
loader was necessary. Indeed I found
it simple to write the program
straight from the keyboard with only
a hazy plan of the outcome. As long
as the main program is located at a
high line number such as 2000, and
plenty of space is left between lines
in this main part to allow for plenty
of conditional Gosubs such as

IFX=2ANDY = 3ANDZ-4THEN

GOSUB (attack by Daleks)
the program can be elaborated ad lib.
G J Langford,
Ickenham, Middlesex.

PURE ARTISTRY

rhe Genie program Top Drawer,
in Your Computer April, has one
slight bug. No matter which key is
pressed, the values of XX and YY
will be unaffected, as the program
always returns to line 20, before
lighting the pixel. Therefore the
values of XX and YY are reset to
their respective initial values. To
cure this rewrite lines 20 and 150
and insert a line 25 as follows:

20 XX = 62: YY - 24
25 SET (XX. YY)
150 GOTO 25
Here is a Genie drawing program,
which requires less than IK of
memory and allows you to control
the movement of a line by using the
four arrow keys. Each key moves the
spot in the direction of the arrow
marked on the key. In addition,
diagonals may be drawn by pressing
two keys together, so if up arrow and
left arrow are both pressed, then the
line drawn will be to the upper left-
hand corner.

As Peek is used instead of InkcyS,
movement continues as long as keys
are held down, rather than one place
moved per press.

John Marshall,

Acomb,

York.

TIGHT WRITING

^►ilent Running in the March
& issue is a good piece of very tight
writing to fit into IK. However it is
easily run in the expanded machine
without removing the RAM pack by
simply lowering RAMtop. I Poked
163$8,0 and 16389,73. This leaves
over 2K usable so that the machine
code runs properly and there is still
plenty left to add a time delay and
automatic rerun at the end. I have
also added a high-score and some
instructions.

Les Simpson,
Elm Park,
Essex. I

10

CL o Pare artistry program

26

X=62 = V= 24

38

SETCX,V)

40

Z=PEEK< 14400)

45

IF Z=0 GOTO 40

50

IF Z<8 OF: Z>8@ THEN 40

68

IF Z = 8 THEN 65 ELSE 70

65

V=V-1 - GOTO 156

78

IF Z = 16 THEN 75 ELSE 80

r-3

V = V + 1 = GOTO 150

80

IF Z = 32 THEN 85 ELSE 90

85

X = X - 1 = GOTO 150

90

IF Z = 40 THEN 95 ELSE 100

95

H =X-1- V = ¥-1 =001*0 150

100

IF Z = 48 THEN 105 ELSE 110

105

X =X-i : V= V + 1 : GOTO 150

110

IF Z = 64 THEN 115 ELSE 120

115

X = X + l: GOTO 150

120

IF Z = 72 THEN 125 ELSE 130

125

X = X + l: V = V - 1= GOTO 150

130

IF Z = 80 THEN 135 ELSE 140

135

X = X + 1; V = V + 1- GOTO 150

140

GOTO 40

156

IF X<0 THEN X = X + 1

ELSE IF X> 127 X = X - 1

160

IF XC0 THEN V = V + 1

ELSE IF V> 47 V = V -1

170

GOTO 30

YOUR COMPUTER, JUNE 1382 13

HEWS.

■ 1 !"*"""

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[ 1

8

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£D □ □ □ O O □ SO ED E3

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'^ ^ SHARP

Sharp colour prints from 3.5K
pocket-computer system

The po 1500 pocket computer
launched by Sharp has 16K ROM
and 3.5K RAM, a $even-by- 1 56 pro-
grammable dot-matrix liquid-crystal
display and a tone generator. The
RAM can be extended by an
optional 4K CE-151 module to
7.5K. A C-MOS eight-bit CPU
allows fast data processing.

Other features include a standard
QWERTY typewriter keyboard and

Text editing

Ztext and LText are word-
processing packages for the ZX-81
which include a text editor and a
formatter/printer. The text editor
allows you to type text in and edit it
while the formatter/printer puts the
text on the screen or ZX printer, and
justifies and formats it according to
commands embedded in the text.

ZText just uses upper-case letters,
but LText caters for both upper- and
lower-case characters. Both pro-
grams, together with a detailed
manual, are available for £7.50 the
pair, including VAT and post and
packing, from Oasis Software,
Lower North Street, Cheddar,
Somerset BS27 3HH. Telephone
0934 743409.

Vulcan alert

V1020 manufacturer Commodore has
linked up with Hendon-based elect-
ronics distributor Vulcan in a bid to
make the Vic-20 available in a wide
range of department stores and
independent outlets. Commodore's
Vic-20 is already sold in all Rumbc-
lows, Laskys, Currys and Deben-
hams stores and will also be on offer
in Dixons shops and 80 branches of
Boots. Vulcan will be responsible for
supplying the Vic-20 to all other
retailers not covered by Commo-
dore's present distribution network.
"Vulcan's role on behalf of
Commodore will be to give new out-
lets a chance to experiment with the
Vic-20 and learn how to sell this type
of product", says Vulcan's managing
director Robert Stein.

an ASCII character set with upper
and lower case. A memory safeguard
prevents accidental erasure of
programs by ensuring that programs
are retained even when the power is
switched off. Its extended Basic
provides two-dimensional arrays,
variable strings, program chaining
and graphics commands, Power is
supplied by cither four dry batteries
or from the mains via a Sharp
adaptor.

A CE-150 four-colour graphics
printer and cassette interface is also
available as an option. Virtually any-
drawing can be printed in red, black,
green and blue, from pic charts to
column graphs. The printer is cap-
able of automatic program, data and
calculation printing. Both the
character size and the lines can be
varied with the lines ranging from
four to 36 digits in length. The
cassette interface enables the
PC- 1500 to be connected to two cas-
sette recorders, which allows inform-
ation to be stored and retrieved on

tape. Sharp is currently working on
further options for the PC- 1500,
including an RS-232C interface and
a software board to act as input keys
in graphs or pictures previously
drawn on a template.

A cassette of 15 applications
programs is available, together with
an applications guide, for £15. The
programs include multiple regres-
sion analysis, simultaneous equa-
tions, numerical integration and con-
version between decimal and base-P
systems. The cassette also includes
two games programs, Slot Machine
and the nautical game Destroyer v.
Submarine.

The PC- 1 500 pocket computer
costs £179.95 including VAT; the
CE-150 graphic printer/cassette
interface costs £149.95 including
VAT; and the 4K RAM CE-151
module costs £49.95 including VAT.
All are available from Sharp Elect-
ronics (U.K.) Ltd, Sharp House,
Thorp Road, Manchester M10 9BE.
Telephone 061-205 2333.

Winners of the national software competition for schools were presented
with their prizes at Bare/ays Bank's head office in London by general
manager Humphrey Norrington — third from the left. The senior
competition was won by Roy Coote, A/an Tomkins, Dean Dennison and
Michael Costin from Robert Clack Comprehensive School, Dagenham,
Essex, with a program designed to assist an interior-design company.
Winner of the junior competition was Truro schoolboy Paul Clark, IS —
second from the left — with a computer system for use in nurseries and
garden centres. The winners of each competition were awarded €400 and
a Kent Software Trophy to be held for one year. The winners' schools
were presented with £1,000 worth of computing equipment The
competition is run by the University of Kent and is designee/ to foster an
awareness among schools of the industrial and commercial uses of
computer systems.

Viewdata on
your micro

Telesoft Tantel, a viewdata
adaptor with RS-232 computer inter-
face, has been launched by Tandata
Marketing in association with
Prestel. Software necessary for up-
and down-loading the Prestel Tele-
software database has been commis-
sioned bv Prestel for the Apple,
ZX-S1, TRS-SO and Pet.

The software will be provided free
to all buyers of the Telesoft Tantel
adaptor except for Pet owners. The
Telesoft Tantel costs £190 plus
VAT from Tandata Marketing Ltd,
Clyde House, Reform Road, Maiden-
head, Berkshire SL6 8BU. Tele-
phone: 0628 7466 L

Lander EPROM

The lm-124 eprom programmer from
Lander Microsystems is designed for
use with the TRS-80 Model 1 Level
II 16K Microcomputer. Housed in a
plastic case, it is supplied complete
with an integral power supply and a
20-pagc users' manual No person-
ality modules are required and all
EPROMs can be fully programmed
in one pass.

The LM-124 software includes a
256-bytc page display, single inter*
page keystroke and full cursor
control. The system is compatible
with EDTASM, the TRS-80 editor/
assembler.

Although designed for the
TRS-80, the LM-124 hardware can
be used with other microcomputers,
provided they have suitable software
and the necessary control signals are
accessible. Adaptors and software
are currently being developed to
allow the LM-124 to be used with
the TRS-80 Model 3 and Genie 1.

As an introductory offer, the
LM-124 is available for £57.50 until
June 12 when the price goes up by
£10 to £67.50. More details from
lender Microsystems, 32 Clock-
house Lane, Collier Row, Romford,
Essex RM5 3QJ. Telephone: Rom-
ford 26325.

Restaurant in
the sky

The takeover of British Airways is
the objective of Airline, one of two
business games for the 16K ZX-83
developed by Cases Computer
Simulations. To take-over British
Airways you must build up your
capital by running your own airline ,
at a profit,

Autochef is similar to Airline, but
the objective of this game is to build
up your company so that you can
take-over Trust House Forte in the
shortest possible time.

Airline and Autochef cost £4.75
each and are available from Cases
Computer Simulations, 14 Langton
Way* London SE3 7TL.

14 YOUR COMPUTER, JUNE 1982

NEWS

Sinclair softens up
the cassette market

Hot on the heels of ihc launch of
Sinclair's new ZX Spectrum — see
Tim Harwell's review on page 20 —
Clivc Sinclair has announced a new
range of software for its predecessor
the ZX-81. The 26 new cassettes will
be available from Sinclair Research
by mail order from May.

Nineteen of the new cassettes have
been developed for Sinclair by ICL,
the Government-backed computer
firm. The remaining seven cassettes
were developed by specialist soft-
ware house Psion,

The Fun to Learn series consists
of eight cassettes covering English
literature I and II, geography,
history, mathematics, inventions,
spelling and music. Each cassette
costs £6.95 including VAT. An add-
itional eight cassettes, costing £4.95
plus VAT each, make up the latest
set of Sinclair Research ZX-81 Super

Programs scries of games, quiz and
conversion programs.

Other cassettes include Bio-
rhythms, a six-level chess program
and Space Raiders and Bombers*
Flight Simulation puts you in the
cockpit of an aircraft and judges
your response to the controls and the
outside world.

All the cassettes need the 16K
RAM pack except for five of the
Super Programs series which only
need IK. These cassettes are avail-
able from Sinclair Research Ltd, 6
King's Parade, Cambridge CB2 1SN.
Sinclair has lowered the price of its
16K RAM pack from £49.95 to
£29.95 including VAT. Sinclair says
the reduction was caused by a major
fall in chip costs. But rising pro-
duction costs have caused Sinclair to
up the price of its printer from
£49.95 to £59.95 plus VAT.

Hi

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£ *

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Record 38,000 queue to visit Fair

OUR 1932 COMPUTER FAIR, held at
London's Earls Court exhibition
centre on April 25-25, attracted
more than 38,000 people over the
three days. This was the largest
attendance ever at any personal

computer fair in Britain. The
Sinclair stand was rushed off its feet
after launching the new Sinclair ZX
Spectrum on the first day of the
Fair.
The ZX Village was also very busy

Thumper bites the dust

The British heat of the Euromouse
Maze Contest, held at the Computer
Fair, was an absorbing battle, The
prc-match favourite Thumper was
beaten into fifth place by Alan
Dibley's T3, Yet another Theseus,
which found its way to the centre of
the maze in a best time of one
minute and 13 seconds.

David Woodficld's Thumper,
which was credited with unofficial
practice times of one minute dead
and one minute and 13 seconds, mis-
took a piece of white tape for a wall
and failed to reached the centre of
the maze. First prize consisted of a
trip to Haifa, Israel, in September,
to represent Britain in the Euro-

mouse Maze final. Second prize was
a Sinclair ZX Spectrum won by Alan
Dibley's Son of Theseus in a time of
three minutes and 21 seconds. Phil
Yeardley of Sheffield halted Alan
Dibley's run of success by taking
third place with Brainy Bricks in a
time of four minutes and 53 seconds.
He was awarded the latest Armdroid
Robot.

Tony Porter's Maisymouse
finished fourth, Alan Dibley's
original Theseus came sixth while
David Buckley's Marvin ended up in
seventh place. All the contestants
received one year's free subscription
to either Practical Computing or
Your Computer,

with microcomputing enthusiasts
keen to discover the latest develop-
ments in ZX-80/81 hard- and soft-
ware. Next year's exhibition will
again be held at Earls Court on June
16-18.

Alan Dibley watches anxiously as T3

Colour board
wins £3,500

Keith purkiss, the 19-year-old who
developed the first colour board for
the Sinclair ZX-81, has won the
£3,500 first prize in the Daily
iTjc/>r«s/Phiiishavc "Get Up And
Go" awards scheme.

The £17,000 award scheme was.
launched in January to encourage*
16- to 21-year-olds to come forward
with their own ideas for a workable
business or project.

Keith Purki$$ set up his own busi-
ness — Haven Hardware — in July
last year to design and market a
range of computer hardware. The
company's products include a pro-
grammable character generator,
rotating key module, I/O port,
memory expansion unit and a full-
size keyboard for the 2X-81. Purkiss
is currently working on nine more
boards, including an inverse video
fortheZX-81.

storms to victory.

YOUR COMPUTER, JUNE 1982 15

DOWNSWAY

ELECTRONICS (UK) LTO

^

Now, you can give your ZX81 more memory than a 48K
Spectrum — for less than £50! If you already have a 16K
RAM pack, of any make and regardless of condition, you
can trade it in for £12.50 against a Downsway 64K Memory,
bringing the price down to only £47.45 (plus £2 p&p),
compared to the Spectrum's price of £175!

Without trade-in, the Downsway 64K Memory costs just
£59.95 plus p&p — still incredible value!

The 64K Memory gives 56K of available memory, and simply
plugs into the 2X81 without needing an additional power
supply, or adding any extra load to the internal 5V regulator.

Should you only need 16K of memory for your 2X81, the
Downsway 16K RAM Pack offers the same benefits of high
standards and low price at ony £24.95 plus p&p.

The $fim, "tow-proMe" styling
of both memories complements
the 2X81, and e spectaJ foam
cushion provides added
mechanise! stebsffty.

NaturaMy, Downsway add-on
memories ere fuBy tested end
guaranteed, but should you be
drss&ttsfted for any reason, fust
return the memory within 14
days for a fuil refund (and your
old 16K RAM peck, where
appropriate).

Pfease effow up to 28 days for
delivery.

Order Form

To: Downsway Electronics (UK) Ltd
Downsway House, Epsom Road,
Ashtcad. Surrey.

Please send me:

ZX81 16K

ZX-MC

• ELIMINATE MACHINE CODE PROBLEMS with ZX-MC -
a new machine code debug/monitor for the 2X81 16K.

• ENTER, RUN £t DEBUG your machine code programs
Independently of Basic commands. ZX*MC resides in RAM,
and leaves you 12!6K of memory to work with.

• SAVE a LOAD your machine code programs AT DOUBLE
SPEED. At last you are freed from storing your M/C in arrays
or REM lines.

• REGISTERS DISPLAY & BREAK POINTS to make

de- bugging easier - PLUS many more useful commands.

• A MUST FOR BEGINNERS h ADVANCED USERS -
concentrate on your M/C programs, not on how and where to
store them.

• ZX-MC is supplied on a high quality cassette, with a
36 page operating manual.

P7 KA l( l ci v AT6rp + p

SCREEN KIT 1

A suite of machine code routines for use in Basic
programs, to enhance your screen display, and create

DATA FILES on cassette. Screen Kit becomes part of your
Basic program.
/m DATA FILES - Save &• Load, at double speed, just the
Basic variables. Load different variables into the same
program, or exchange variables between programs.

• DRAW A BORDER • KEYBOARD SCAN

+ FLASHING CURSOR

• CLEAR PART OF SCREEN •LOAD ANY CHARACTER

TO WHOLE SCREEN

• INVERT VIDEO OF PART OF SCREEN • MEMORY LEFT

• CLEAR SCREEN BY SCROLLING UP, DOWN, LEFT
OR RIGHT ind. VAT & P + P

• Supplied on cassette with instructions, tO. /U (C.W.O.)

Send SAE for more details.
Allow up to 14 days for
delivery.

Programs available mail order
only. Please make cheques/PO
payable to:

6, Corkscrew Hilt, West Wickham.
Kent BR4 9BB

Qty

Item

Price

Tout

64K Memory at special
trade pnee (my old 16K
RAM pack is enclosed)

£47,45

64K Memory at normal
poce without trade- in

£59.95

16K RAM Pack

£24,95

Post and Packing

£2 00

Total

£

My cheque /P.O. /Money Order is enclosed
NAME:

ADDRESS:

YCS

piiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiniiiiiiiiiiiiiiiiiiii|

| Educational Software for |

1ZX81 - BBC-ZX82I

Programs for learning at home ~

m and at school. j

I • Written by teams of teachers

1 and programmers. I

• Primary — secondary — FE. j

| • English, French, geography,

| maths, sciences, etc. -

1 • Excellent reviews. i

= Send s.a.e. for details to:

1 AVC SOFTWARE

1 PO Box 41 S

I BIRMINGHAM B17 9TT

m

16 YOUR COMPUTER, JUNE 1982

COMPUTER CLUB

Computer Club is here to encourage you to start your own local computer club or, if one already
exists, to join it and become involved. Each month we will devote the page to new ideas from
local clubs. We would like to hear of anything which has made a club a success, or of any
projects or programs you are developing.

BBC hits East London

The books' days are numbered
at Harrow Green library. On the
second and fourth Tuesday
evenings of every month, local
micro enthusiasts gather there
to develop their expertise.
Brendon Gore went along to
check out the East London
Amateur Computer Club.

JANET CORNISH, one of the 12 who founded
the club in 1978, introduced the BBC
Microcomputers, and pointed out that the
Model B had eight display modes, while the
Model A only allowed modes 4,5,6 and 7.

The three Model Bs at her disposal proved
that Acorn is finally clearing some of its back-
log. Janet Cornish used different colour modes
to create a variety of shapes from a simple map

to multicoloured flashing triangles. In mode 5,
for example, colour 1 selected a red fore-
ground and colour 129 selected a red back-
ground. Similarly, colour 2 resulted in a
yellow foreground and colour 130 created a
yellow background. The CLS command
cleared the screen to the background colour.
The Draw command, which can be used in
modes 0,1,2 and 4, enables you to draw a line
from the pre-set cursor position to the
specified x and y values. Thus Move 300,200
and Draw 1000,1000 sets the cursor position
and draws a line to the required spot on the
screen. The screen is addressed as x, points
0-1279. and y, points 0-1023, she noted.

Character redefinition

VDU can be used to redefine the character
set, change the colours in different modes and
to set up your own text windows. VDU 4
separates the text and graphics cursors,
enabling you to operate both inside and out-
side the text window, while VDU 5 reverses
the process.

The talk was warmly received by the 40
members present. Club chairman Fred Linger

Local society news

Laserbug

LASERBUG IS the London and South East
Region BBC iMicrocomputer Users' Group. A
newsletter edited by Trevor Sharpies aims to
share ideas and discoveries about the BBC
Microcomputer. Laserbug also hopes to
encourage the setting up of local groups under
its banner. A year's subscription to Laserbug
costs £12. For further details write to
Laserbug, 4 Station Bridge, Woodgrange
Road, Forest Gate, London E7 0NF.

Vic-20 User Group

Matthew stibbe of The Lawn, Lower
Woodficld Road, Torquay, South Devon,
hopes to start a Vic-20 user group and software
library. Anyone wishing to borrow or contri-
bute programs for the Vic-20 should contact
Matthew Stibbe at the above address.

Norwich BBC User Group

MEETINGS OF THE Norwich and District BBC
Microcomputer User Group are usually held
twice a month at the Norwich City College.
They consist of either a computer workshop or
a talk about some specific area of micro-
computing. For more details contact Paul
Beverley at Room 12a, Norwich City
College, Ipswich Road, Norwich, Norfolk,
NR2 2LJ.

North Wiltshire Club

North Wiltshire Computer Club meets at
Holt village hall on the second and fourth
Wednesdays of each month. Everyone is
welcome, from the absolute beginner to the
expert, on payment of 50p entrance fee. More
information from Matthew Jones, Finhills,
Bowood, Calne, Wiltshire, SN1 1 0LY.

announced forthcoming events. Dick Marsh
will talk about screen editing on June 8, while
Mr Parran will discuss the effects of com-
puters in education on July 1 3. Peter Wright is
expected to throw some light on the subject of
EPROM burning on August 10.

A previous talk on the subject of Forth,
given by Mike Curtis of the Willesden College

Mode

Graphics

Colours

Text

640 by 256

2

80 by 32

1

320 by 256

4

40 by 32

2

160 by 256

16

20 by 32

3

—

2

80 by 25

4

320 by 256

2

40 by 32

5

160 by 256

4

20 by 32

6

—

2

40 by 25

7

Teletext

2

40 by 25

BBC graphics mode.

of Technology, spawned a Forth interest
group inside the club. Other club activities
include a library of books and programs, and a
monthly newsletter edited by Ed Lepley and
Jim Turner. The newsletter carries inform-
ation about the club and its members, tips on
hardware and software problems and lists
future events. A monthly puzzle, for club
members only, is also a popular item.

The March puzzle consisted of writing a
Basic program to input any two numbers and
print them in ascending order of value. To
make it a little more difficult entrants were not
allowed to use Calls to machine code, USR,
Peek, Poke, Data statements or calls to other
monitor routines. In addition, entrants were
not allowed to use Basic comparative
commands such as If — Then or On — Goto
or Gosub.

The simplest solution to the puzzle, pub-
lished in the club's April newsletter, consisted
of the following program:
10 INPUT "Enter 2 numbers";A,B
20 PRINT{A + B-ABS(A-BH/2
30 PRINT <A + B + ABS(A-B»/2
40 GOTO 10

Club membership costs £4 a year for adults
and £2 a year for students and old-age
pensioners. More information is available
from the club's publicity officer Jim Turner,
63 Millais Road, London El 1 4HB. ■

YOUR COMPUTER, JUNE 1382 17

Memotectts New Memoiy^stem for the ZX81

It grows as youprogress

Memopak 16K Memory Extension

-£3938iiKiWr

It is a fact that the ZX81 has revolutionised home computing,
and coupled with the new Memopak 16K it gives you a
massive 16K of Directly Addressable RAM. which is neither
switched nor paged. With the addition of the Memopak 1 6K
your ZX81 s enlarged memory capacity will enable it to
execute longer and more sophisticated programs, and to
hold an extended database.

The 1 6K and 64K Memopaks come in attractive, custom-
designed and engineered cases which fit snugly on to the
back of the ZX81 . giving firm, wobble-free connections.
See below for ordering information.

Coming Soon.* m^k™

;tt*pfterak W-fiES GRAPHICS

Mcfnotech HhRc* Graphics CENTRONICS IF,

Centronics Interface ana Software Dover*
Memotetn Digitising Tablet RS232 interface

All these products are designed to fit piggy-back' fashion
on to each other, and use the Sinclair power supply.
WATCH THIS SPACE for further details. We regret we are as yet
unable to accept orders or enquiries concerning these products
- but well let you know as soon as they become available.

How to order your Memopak.

By Post: Fill in ihe coupon below and enclose your

cheque'P.O /Access or Barclaycard number.

By Phone: Access-'Barclaycard holders please ring

Oxford (0865) 722102 (24-hour answering service)

nenopfiK 64K

ftCftOPfiK 64B

"

Memopak 64K Memory Extension

*7WK)tacLW

The 64 K Memopak is a pack which extends the memory of
the ZX81 by a further 56K ? and together with the ZX81 gives a
full 64K. which is neither switched nor paged, and is directly
addressable. The unit is user transparent and accepts basic
commands such as 1 DIM A(90Q0).

BREAKDOWN OF MEMORY AREAS

0-8K . . . Sinclair ROM

8-1 6K . . This section of memory switches in or out in 4K

blocks to leave space for memory mapping, holds its

contents during cassette loads, allows communication

between programmes, and can be used to run assembly

language routines.

16-32K . . . This area can be used for basic programmes and

assembly language routines.

32-64K . . . 32K of RAM memory for basic variables and large

arrays.

With the Memopak 64K extension the ZX81 is transformed into a

powerful computer, suitable for business, leisure and

educational use. at a fraction of the cost of comparable

systems.

Unique 3 month trade-in offer!

When your programming needs have outgrown the capacity
provided by 1 6K RAM, and you find it necessary to further
extend your ZX81 "s capacity, we will take back your 16K
Memopak and allow a discount of £15.00 against your
purchase of our 64K model "

* We reserve the right to reject for discounting purposes, units which
have been either opened or damaged « any way

i

O
<

S

E

Please make cheques payable to Memotech Limited
Please debit my Access/Barclaycard* account number

I

Please send me:

'Please delete whenever does n<x apply
SIGNATURE

DATE.

16K RAM. Assembled

64K RAM, Assembled

Quantity

Price

£39.95

£79:00

Postage

Total Enclosed

NAME.

ADDRESS.

Total

£2.00

I
I .

■ We want to be sure you are satisfied with your Memopak - so we offer a 1 4-day money back Guarantee on all our products.
Memotech Limited, 3 Collins Street, Oxford OX4 1XL, England Telephone: Oxford (0865) 722102/3/4/5

*

18 YOUR COMPUTER, JUNE 1982

r

3m us 83

'"■ ...aw i» » — sm w .' ... t.. i__

mm mm mm mm mm mm w
- ; »a bk: in on 2 ° 3B *

^•■jw MHB 4BMI H^W 1MHB Hmv 'itsB - *•*- ■-

f

Give me

one good reason why I should

choose a VIC 20 home computet:"

1. VIC is outstanding value
for money No other colour
home computer can give so
much for under £200.

2. Total standard memory
25K made up of 20K ROM and
5K RAM.

1 Fully expandable to 32K
of user RAM.

4 Microsoft Basic inter-
preter as standard.

5c Accessible machine
language as standard.

6l Connects direct to
monitor or standard television.

7 Full size typewriter-style
keyboard.

8. Full colour and sound.

9. All colours directly con-
trollable from the keyboard.

10. 62 predefined graphic
characters direct from the
keyboard.

11. Full set of upper and
lowercase characters.

12. 512 displayablc characters
direct from the keyboard.

11 High resolution graphics
capability built into the
machine.

14. Programmable function
keys.

Vx Automatic repeat on
cursor function keys.

16. User-definable input/
output port.

17 Machine bus port for
memory expansion and ROM
software.

18. Standard interfaces for
hardware peripherals.

19. VIC 20 is truly
expandable into a highly
sophisticated computer system
with a comprehensive list

of accessories ( see panel below) .

20. Full range of software for
home, education, business and
entertainment on disk,casscttc
and cartridge.

Accessories include:

• Cassette tape unit.

• Single drive 5J' floppy disk unit (1 70 K bytes
capacity).

• 80-column dot matrix printer.

• 3K, 8K and 16K RAM expansion cartridges.

• Programming aid packs; machine code
monitorcaitridgcpmgrammers'aidcartridgc^high
resolution graphics cartridge.

• Plug-in conversion box for a full 32K,
40-column x 25 lines VIC including Prestel com-
parability

• Prcstcl/Tantel interface package.

• RS 232C communication cartridge.

• Memory expansion board

• 1 EEE/488 interface cartridge.

• Joysticks, light pens, paddles 3nd motor
controllers.

21. Books, manuals and learn-
ing aids from Teach Yourself
Basic to the VIC programmers 7
reference guide (a must for
advanced programmers).

22. Full support for VIC owners

- their own magazine 'VIC
Computing' as well as a national
network of VIC user groups.

21 National dealer network
providing full service and
support to VIC owners.

24. Expertise and experience

- Commodore are world
leaders in microcomputer and
silicon chip technology.

25. Commodore is the leading
supplier of micro-computers
in the UK to business, schools,
industry and the home.

26. VIC 20 is the best-selling
colour home computer in
the UK.

How many reasons was it
you wanted?

ft commodore

VIC20

The best home computer
in the world.

FOR MORE INFORMATION ON THE VIC 20, TELEPHONE OR WRITE TO: COMMODORE INFORMATION CENTRE,

BAKER STREET, HIGH WYCOMBE, BUCKS. TEL: SLOUGH 79292.

REVIEW

SINCLAIR

The new Sinclair has arrived at
last — a book-sized micro-
computer with colour and
sound and an extended version
of ZX Basic. It came through
its test well ahead of the
competition but, as Tim
Hartnell found, even Sinclair
Research cannot work
miracles.

Launching THE SPECTRUM, Olive Sinclair
confessed that there had been considerable dis-
agreement within his organisation over the
name of the new computer. "At one point", he
said, "we thought of calling it 'Not the BBC
Micro*". In March last year, Sinclair
unleashed an angry tirade against the BBC for
giving Acorn the right to make the computer
for the TV series, saying that he had told the
BBC he could produce a computer — within
their specifications — for just over £100. The
ZX Spectrum is the fulfilment of that promise.

The Spectrum has eight colours, a built-in
sound generator and loudspeaker, and the
closest Sinclair Research has come to a "real**
keyboard. Its specifications exceed those of the
Model A BBC machine, and come close to the
Model B in many areas. At just £125 for the
16K model, the Spectrum is the same price as
a ZX-81 w ? ith 16K pack when first launched.
With 48K the Spectrum" costs £175.

The Spectrum uses a * 'superset" of ZX-81
Basic, and any ZX-81 program can be typed in
with the minimum of changes; ZX-81 tapes
cannot be loaded into the Spectrum. The new-
computer loads and saves much more quickly
than does the ZX-81, at 1,500 baud as against
around 250, and the upward compatibility of
listings should mean a lot to organisations like
Muse which are building up a library of
educational ZX software. Publishers of ZX
literature or ZX software breathed a sigh of
relief on hearing that ZX-81 listings could be
entered directly.

The Spectrum works in upper- and lower-
case letters, and does so like a typewriter:
capital letters appear only when you use the
shift key. The computer does not differentiate
between upper and lower case when naming
variables — so AS is the same as a$ — and will
ignore spaces in variable names.

The range of characters is standard, and
symbols such as ! and # arc available on a ZX
machine for the first time. There is a range of
three different curly brackets and a cute little
© copyright sign.

The © sign, and the w r ords "Sinclair
Research Ltd'* appear on the screen in black
letters on a white ground when you first turn

20 YOUR COMPUTER, JUNE 1982

it on* Pressing New LList or Copy produces
some remarkable flashing-border displays, and
in Save and Load you arc treated to a lollypop-
striped screen in reds, blues and yellows.

The error codes are fascinating, and in
English rather than the odd little numbers and
letters of the ZX-80 and ZX-81. If all goes well
in a Load, a Save, a program execution or
whatever> the computer prints "OK" at the
bottom of the screen. If you manage to make it
swallow an incorrect line or parameter —
which is difficult to do, because all lines are
checked for syntax before being accepted into
the main body of the program — the computer
prints the delightful line

Nonsense in BASIC.
Whoever wrote the ROM had a sense of
humour,

There is much in Spectrum Basic to tempt
you to enhance your programs. It includes
Beep, a single-channel "music" command
with both duration and pitch under user
control, Ink to determine the colour of the
Print output and Paper for the background
colour. The Border command allows the area
round the main display to be independently
coloured and changed, Flash sets all Printed
material flashing into its inverse colour, and
Bright intensifies the colour of selected pixels.

All commands can be put into a Print? or
Input statement, such as

PRINT PAPER 4;INK2;AT 10,10; 'hi there"
for red letters on a little green strip just under-
neath the letters, or can be entered within the
program to alter everything that comes after-
wards. A line reading Ink 1 followed by Paper
6 will make all printed matter blue, and the
whole screen yellow; Border 2 puts a bright
red frame around the screen. The colours are
easy to use, and the keys are clearly marked,
with the colours they represent.

The screen is memory-mapped and the
computer runs as fast as the ZX-81 does in
Fast mode, but with a rock-steady permanent
display. Nevertheless, the ZX Basic is
considerably slower than BBC Basic. High-
resolution graphics of 256 by 192 can be
achieved, and the Plot command works on a
grid this size, but the control is not available to

i I —

ZX Spectrum

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the same resolution. Colour works on a grid of
32 by 22, the same grid as for letters. Read,
Data and Restore are available, as well as Dcf
FN and FN, and enhance the capabilities of
the computer considerably.

It is obvious that Sinclair has listened to
those who have criticised some shortcomings
of the ZX-80 and ZX-81. The Load and Save
procedures on the earlier machines, in
particular, left a great deal to be desired. The
Spectrum Loads in blocks, sets the record

level automatically and suppresses noise. Once
you think you have a program successfully on
tape — and before you New it from the
computer — you can play it back into your
computer using the Verify command, to make
sure it is there safely. The very first program I
attempted to save on the Spectrum Saved,
Verified and Loaded successfully at first
attempt.

The new Load and Save, along with the fact
that the memory can be relied on not to drop

out unexpectedly, make working with the ZX
Spectrum a pleasure. The awful fear that your
carefully keyed-in program is about to vanish
into thin air has been banished. The 16K or
48K memory is permanently fixed inside the
Spectrum. You cannot use the ZX-81's 16K
pack, though the new computer docs operate
the ZX printer.

The ZX Spectrum is small and flat, rather

wider than the ZX-81 but not as deep. The

(continued on next page)

YOUR COMPUTER, JUNE 1982 21

(continued from previous page)
keys arc rubbery, and appear to press on to a
standard ZX keyboard. You can use them
without looking at the keyboard, once you
know your way around it, and a touch-typist
will soon feel at home. The key action is
positive — although you need to squeeze the
keys rather than press them — and there is no
need to keep checking the screen to sec that
each keystroke has been entered.

AH keys have auto repeat, which is a boon
for running out parts of lines or for moving
the cursor along the long line you wish to edit.
The Spectrum makes a clicking noise while
auto repeat is working. If you start the auto
repeat with a key which requires Shift such as
Delete you can take one finger off the Shift
and just leave it on the Delete key once the
auto repeat is underway. The Edit facility is
the simplest to use of any computer on the
market, it is better than that on the BBC
Micro, except that you cannot join together
parts of separate program lines.

Symbols and keywords

The keys on production models are to be
light-blue, with the alphanumeric symbols and
keywords marked in white. Function symbols
such as ?, At, Then and + are in red.

Sinclair invented the "one-touch key 1 *
system for the ZX-80, which ensured that the
computer knew that the first key pressed after
a line number, or after the word Then, would
produce a keyword, such as Let, Print, Poke
or Goto, This meant that programming was
fast and positive. The ZX-81 demanded a
sequence of key presses — such as Shift, then
Function, then a key — to get the results you
wanted. Sinclair is obviously wedded to the
one-touch entry system, but it is really not
suited to the Spectrum. The sequence of key
presses required for Ink and Atn, for example,
requires rhc same number of key presses as
would be needed to type the word in directly.

There are now two Shift keys, a white one
and a red one. The white one works like the
standard shift key on a typewriter, turning
lower-case letters into capitals and, in the
Graphics mode, producing the graphic rather
than the number from the keys 1 to 8, The red
Shift key, on the bottom right-hand corner of
the keyboard, is used for words such as At, Or,
And, Then and Step, along with the full stop,
the colon for multi-statement lines, and the $
sign. The ■ sign is also accessed by using this
shift, then pressing L> but as these are next to
each other, you will soon find yourself press-
ing both keys at once with your right hand to
enter the = sign.

You must press both shift keys at once,
followed by another key. press, to enter words
such as Int, Rnd, Chr$ and Codes. Other
commands, such as Ink, Paper and Beep,
require both shift keys to be pressed at once,
then the red one to be held down while the
relevant key is pressed.

Unfortunately, the command New is as easy
to access as Print and Goto — no Shift keys or
juggling needed. This is sure to result in
programs being wiped accidentally, especially
as New lies between Copy and Plot. By
contrast, the harmless Stop command, on the
same key, needs two key presses. Designing
the New like this suggests that not enough
thought has been given to human behaviour.

Other aspects of the keyboard show more
care in their design. The Then and Goto are
on the same key> as these are often accessed
one after the other; the same goes for For and
To. There is a single apostrophe — a wise
lesson learned from Atom and BBC Basic — to
move the Print statement down a line, so

PRINT ' ' "HI"
will skip two lines before printing the word
"HI".

The List command takes some getting used
to. Pressing List will give you a page of
program, then the message

scroll?
will appear in the bottom left-hand comer.
Pressing any key except "n" allows the listing
scroll to continue, page by page. The current-
line cursor, an inverse > symbol on the ZX-8 1 ,
has been replaced by the same symbol
displayed in normal mode. It is not
particularly easy to see, and you can spend a
lot of time running your eyes up and down the
column after the line numbers to find it. Using
List n to find a line you have requested is
almost comically difficult.

The Beep command is simple to use, and the
volume from the internal speaker is adequate.

The sound output can be tapped from both
the Mic and Ear sockets at the back, to drive
an earpiece or to feed into an amplifier, The
word Beep is followed by two parameters. The
first is the duration of the tone in seconds —
fractions of a second, such as .05 or 17/36, are
also accepted — followed by a comma,
followed by the frequency. Middle-C is a 0, so

Beep 1,0
will play middle-C for one second. Higher
numbers produce higher notes, with negative
numbers for notes below middle C. There is a
range of around 130 semitones, and fractions
of a tone are accepted.

The graphics are a development from those
of the ZX-81. AH the standard ZX symbols are
there, made from quarters of a character
square, with black and grey, along with their
inverses. The new Draw command draws a
remarkably fine line from the co-ordinates of
the Plot command and can therefore be used
as a substitute for Move. The Draw command
can also be used to draw parts of circles by-
adding a third parameter, the angle to be
turned through. The Circle command —
naturally enough, it draws a circle — needs
three parameters: the x and y co-ordinates of
the centre, and the radius. The circles drawn
appear very close to true circles, especially if a
fairly large radius is used.

Lower-case letters

The lower-case letters, formed on an eight*
by-cight character grid, are fairly good,
although the descenders only go down one
pixel.

You can define up to 21 of your own
characters, using a remarkable function called
Bin — for binary — which allows character
shapes to be Poked into position. The new
character can be assigned to any key. ChrSS, is
a back-space which does not erase the
character, and you either overprint, using the
command Over, or underline. Far more
sophisticated than on the ZX-81, the
Spectrum graphics will prove a boon for
improving screen and printer output, although
they will also be more difficult to master.

It is good that Sinclair has decided not to kill
the ZX-81 as it is still the ideal first computer.
Those who know how to program a ZX-81
will find they can gain reasonable facility with
the Spectrum within a couple of hours. After
countless hours staring at the black, greys and
whites of the dumb ZX-81, the brilliant
colours and the Beeps from the Spectrum will
ensure that even your dullest programs at least
look interesting.

CONCLUSIONS

■ With powerful colour and sound
commands, the ZX Spectrum is a
remarkable computer, exceeding the
BBC Model A in specification.

■ its use of a Basic very similar to that of
the ZX-81 provides a ready-made
source for software, though ZX-81
tapes cannot be loaded into the
Spectrum.

■ Programs can be saved and loaded
without the problems which plague
the ZX-81. Built-in memory means
that sudden program loss should no
longer be a problem, but ill-

considered keyboard design means
that programs could still be lost by
inadvertently keying New.

I The moving-key keyboard is an
improvement on the touch-sensitive
board.

I The one-touch entry system, retained
from the ZX-81, is not suitable for the
Spectrum and leads to complicated
multi-shift operations when keying
some functions. It should have been
discarded.

I Despite minor faults, the Spectrum is
way ahead of its competitors. There is
certain to be a rush for orders.

22 YOUR COMPUTER, JUNE 1382

ZX81

16K PACK 123

Pack 1. 2 €r 3 include all of:

AIR TRAFFIC CONTROL: Animated radar screen of busy airport shown. You
mutt bring ptanes into land; INVADEftS SELFPLAY; PH0N6S00K - keep
friends' and relatives numbers on cassette. COMPUTER DATING, who will it
pick for- you and those around you for a laugh, ADVENTURE ATLANTIC: you
may become very rich or marooned forever BREAKOUT: SQUASH:
LANGUAGE TRANSLATOR: translates any European language to any other,
COMPUTAPUNT: predict horse races and footbaifl pools with you ZX.
IN DISCO, video roadracer. DRAUGHTS computer chequers, with kings.
BATTLESHIPS, nautical naval battle at home. MASTERMIND: brain teaser,
see if you can beat a mtcroelectroic mind.
THIS MASSIVE PACK OF SOFTWARE IS ONLY £5,00

i&t* ZX ADVENTURE

A brand new release, this package of adventures written in Basic and Machine
Code are the best value and quality available. Just compare them with others!

1 * GOLF: one or two players have a matchplay off with handicaps and progress
around an 18- hole course which is superbly detailed with bunkers, lakes, trees,
bushes and greens. We think you will agree this game has the best graphics
available for the ZX81.

2. OAMSEL IN DISTRESS: you are the knight in shining armour, your quest is
to ride to a vast castle and rescue your princess and release her from the
dutches of Bn evil witch. You must dream up a spell to destroy the old witch
and collect enough go*d to bribe the 9uards. A very Bewitching Adventure
program.

3. STORM THE TOWER: as the General of a medieval army you must deploy
your arms and men so you can attack an enormous castle with a huge tower.
You must build armaments and prepare for the correct hour to attack but
beware of rearguard action and consider intelligence reports with care!

ADVENTURES £8.00

ZX BUSINESS SYSTEM

Now installed in many businesses, comes with PURCHASE, SALES LEDGER
for 100* entries per week, does daybook analysis, VAT met. and excL. totals,
password protection plus many more excellent features. You also get a STOCK
CONTROL. MAIL LIST and PH ON E800K. Easy to use, designed for everyday
small businesses. Includes instruction book and tape. £17.00 incl. VAT.
And does the job of systems costing hundreds of pounds.

ZX AUTOCODER

Writing machine code?

Some love it, some hate it but AUTOCODER just gets on with it. Helping you
produce machine code programs from BASIC. Easy to use and very helpful,
Converts PRINT, PRINTAT. IF THEN, GOTO. GOSUB, LET INKEY$. POKE.
PEEK. CLS, etc.

ALL £5.00 Inci.

MORE DEALERS ARE INVITED

VIC SOFT 7 includes all of:

DEATH RACE 2000: You must runover as many old men and dogs as you can

without crashing into parked cars.

MOROIDS: The Asteroids will try to crash into your Astronaut, you must keep

him alive — very fast graphics.

WARLORDS: Defenc your castle against a giant boulder that is crashing

around destroying enemy tons.

BREAKOUT: The noisiest and most colourful you've seen.

SQUASH: Features on-screen scoring, and test your reflexes.

SOUNDS: Menu driven sound synthesizer program.

MASTERMIND: Can you beat a multicolour mtcroeiectronic mind.

ALL programs use the full sound and colour capabilities of the VIC to the

utmost.

ALL FOR £600

ATOM

ATOMSOFT 4 includes all of:

ASTRO BATTLE ZONE; You view the earth below your space, suddenly UFOs
come at you, the engines roar as you climb to the stars.
DEFENDER: Thrust, laser, cHmh, fire at enemy, Superbry detailed.
TRIDENT: A superb game, you are a sub-commander. Realistic sonar sound
effects, and the 30 graphics of enemy ships appear, you must fire torpedos,
STAR TREK: Rest version available. Sound effects in animated battle
sequences. You need a 12K ATOM as all use Hires memory area.

ALL AT £7.00

SUPER SOFTWARE

AVAILABLE FROM
CONTROL TECHNOLOGY

NEW RELEASE
Trident (Acorn Atom) Death Race 2000 (Vic 20)

t- rvt:s 3

Air Traffic Control (ZX81) Warlords (Vic 20)

C 3 4, a

o a a no l t

s 3 a e s

t. &IOK CS?PG

eu ~^~

IRCCTIOM O? N
C IGHT M? O

CLOCITV V?

Moroids (Vic)

1

Breakout (Vic 20)

Astro Battle Zone
(Acorn Atom)

mm

Draughts (ZX81)

f*&^orrc>n

Maze of Death (ZX81)

fiCCDEFC-H

'OUR UR5T MOVE UR5 TO C,
'MI5 HOUC fftOM

Breakout (ZX81 )

iUdllll

NOW AVAILABLE

Countryside £7.00

EARLY WARNING, BBC computer version

of missive command C7.00

Business Systemm £17.00, Disassemoler £5.00

All prices incl. VATR and p€rp. Pfease send to;
CONTROL TECHNOLOGY, 39 Gloucester Road
Hyde, Cheshire SK14 SJG (061-368 7568).

Please send me as soon as possible the following:
□_ £_

Defender (Acorn)

Fruit Machine
(Acorn Atom)

YOUR COMPUTER, JUNE 1982 23

Which breakout bat
moves too slowly to
catch the ball?
Which version of
space invaders is so
tinny that it has
become known as
"the massacre of
the saucepans"?
Boris Allan answers
these questions and
many others as he
and his dedicated
band of testers sort
cassette and
cartridge programs
for the Vic into the
good, the bad, and
the ugly.

A FEW programs on cassette could cost as
much as the 300 programs provided by a
year's subscription to Your Computer or a
book of listings such as What to do when you
hit return by People's Computer Company or
Basic computer games by Creative Computing.
At about £6, it takes only 22 cassettes to buy
another Vic, and 10 or 11 to buy a ZX-81 to
extend your experience.

Assessing true value

The cost of most of these programs is even
more surprising when one considers that some
very good disc-based Adventure programs for
larger microcomputers cost only £15 — and
some of those programs have really excellent
graphics. Given the quality of the majority of

programs tested, and taking into account the
cost of the cassette, and postage and packing,
to sell them at more than £1.50 could reason-
ably be viewed as expensive.

Obstacle or Maze is probably the most
popular games variant. These are games in
which you have to find your way through a
maze or a minefield where you must dodge

various obstacles which arc fixed or moving,
They include Bug-Byte's Vicmen, in our view
the best version, at one extreme and Abacus*
Maze of Death, the least impressive, at the
other. Some programs had wrap-around —
that is, it was possible to disappear on the
right-hand side of the screen only to appear
immediately on the left. It was not possible,
however, to disappear at the bottom to
reappear at the top. This wrap-around often
seemed uninentional, and is easily explained if
you study the way the screen is organised on
the Vic.

On the Vic, the screen is arranged in 23 lines
of 22 characters, and each location on the
screen is given a number. For four lines of
four characters, the numbers might be:

24 YOUR COMPUTER, JUNE 1982

SOFTWARE

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

So, moving along the top line from left to
right, to go to the right of the top-right
location, 35, is to move to position 36, which
is on the second line down, on the left. To
move upwards in a straight line one subtracts
4, 45, 41, 37, 33, and so one does not wrap-
around at the bottom. This facility is used to
greatest effect in Vicmen.

Variations on a theme

Breakout programs are variations on the
"knock bricks out of a wall 11 theme, and none
of the ones tested is an improvement on a
game in Integer Basic for the Apple II —
though that game uses paddles or joystick.
Most of the programs in this category strive
for originality in many ways, but why change
from the best version? All these programs used
keys, and in at least one case — Blastout 1
from Neme Software — the bat moved so
slowly that it could not catch up with the ball.

The breakout style of program uses real-
time control, as do some of the maze or
obstacle programs: real-time control is where
the user has to manoeuvre in a continuously
varying situation. This category includes
various types of road race, landing a spaceship
safely by use of a visual display — not to be
confused with an older type of program called
Lem in which the only useful information is
height, speed, and fuel. Perhaps the best of
this category is the Commodore cartridge
Road Race and the worst is probably Monaco
GP from Abacus.

In the space invaders or war games category
we have all the many variants of space
invaders, and the various other shooting
games — some played against the computer
and some against an opponent. In our view,
by far and away the worst program was Bridge
Software's Vic Invaders — it was suggested by
one of the test panel that it be renamed "The
massacre of the saucepans" — while

dK'tronics' Rox and the Commodore cart-
ridge Avenger seemed to be the most popular.

One of the cassettes in the intelligent games
section, Line Up 4 from Terminal Software,
made the most favourable impression because
it consistently won a test of intellectual skill —
it is a simulation of the popular game where
you have to connect four counters in a row. An
intelligent game is one such as chess which
requires thought and not dexterity. If a
noughts and crosses program is supposed to be
at all intelligent, a good trap is to play top
right. It will then play in the middle, and so
you choose bottom left: most programs will
then move to either top left or bottom right,
and so lose — both Noughts 1 and Noughts 2
from Neme do.

The logic and mathematics programs

include number guessing games, or games of
logic such as Mastermind. None of the
programs tested provided the player with any
real challenge. They were the Neme Master-
mind and Save Sum City, Abacus* Petals
Around The Rose, Mastermind from Control
Technology, and the PR Software Logic and
Pickup Game.

Some of the programs are best considered as
demonstrations of what you can do with your
micro: for some we cannot think of any other
reason for their existence. The Commodore
cartridge Super Slot, for example, is an
ostensibly tiresome slot-machine program but
which has graphics effects that we had to
admit were good. Many of the programs on
the Commodore cassette Introduction to Basic
Pan 1, arc demonstrations, and some like

Hangman and Speedtype were enjoyed for
themselves.

We shall now consider some of the most
highly recommended programs. The first is
Vicmen which was supplied by the Byte Shop,
Manchester. Vicmen is produced by Bug-Byte
and costs £7. It is a version of an arcade game
called Puckman, and is a real-time maze
program with excellent graphics. Vicmen is a
skilful game which consists of trying to gobble
spots before being caught by ghosts, though at
times you can chase the ghosts to turn them
into eyes. The reason it is so successful is that
it is different, not too complex, and fun to
play.

Simple addiction

Blitz might be classed as a space invaders or
war game, because it consists of a bomber
flying over a town again and again. At every
pass, it reduces attitude, until it runs into a
building. To stop it crashing you must flatten
the buildings by dropping bombs, but only
one bomb is allowed in the air at one time. It
sounds simple, but it becomes almost as
hypnotic as Vicmen. Blitz is produced by
Commodore and costs £4.99 — a very good
example of how you do not have to be complex
to be addictive.

Line Up 4 is definitely an intelligent game.
It is a simulation of a game of Connect 4 — if
you are not wary, or not sufficiently good, it
will win. An interesting extra are the timings
of how long you took, and how long the Vic
took. It beats you, and then boasts about how
quick it is. A well-presented program with
good, clear instructions from Terminal Soft-
ware.

These are far and away the best games, but
there are others which are reasonable — we
felt, however, that a program had to be
exceptional to command the prices being
asked. These three programs were the only
ones for which there was unanimous acclaim,
and it is worth asking why they had this
universal popularity.

They are successful because:
■They are very simple in conception, with no

gratuitous complications.
■They are not like any of the other games.

■ Because listings of these games are not easily
available, their themes are not hackneyed.

■ There are no bugs in the programs; they were
not too simple to play nor were they too
difficult.

One can also learn from the games we felt to
be the least successful. Bridge Software's Vic
Invaders, for example, at £6.50 is too easy, the
invaders do not advance, there are no mystery
ships, the base at the bottom zips along at
rocket speed, and the invaders do not speed up
when only a few remain.

Fiendishly clever

Petals Around The Rose is a number
guessing game with a difference — it does not
tell you the rules. Consequently the user can
never be sure if the game is fiendishly clever
because he f can ! never know what he is
supposed to be doing. At £6.95 from Abacus
Programs, it might not seem worth the effort.

At the end of the review of the Games Pack-
age from Neme Software — £5.50 for five
programs, or £9 for the set of 10 — was
(continued on next page}

YOUR COMPUTER, JUNE 1382 25

(continued from previous page)
written "Keep Clear". This becomes under-
standable when you discover that the program
Pontoon does not recognise pontoon, We were
unable to tell the difference between Noughts
1 and Noughts 2, and the bat seemed incap-
able of catching up with the ball in the Neme

version of Breakout. It can be seen that the
programs were trivial and, what is worse,
poorly de*bugged.

We would advise anybody buying programs
either to see them demonstrated first, or to
obtain a written undertaking that the program
can be returned if unsatisfactory.

Company

Program

Category

Comments

Price

Neme

Games Package:

Trivial and

Five for £5.50

Software

Pontoon

D

poorly de-

10 for £9

Mastermind

L/M

bugged

Shell Game

D

Noughts 1

IG

Noughts 2

IG

•

Clocks

D

Black Holes

O/M

Save Sum City

L/M

Blastout 1

B

Blastout 2

B

Sonic Patterns

D

High resolution

D

Fair

£7.50

/character package

Songmaster

D

Fair

£6.50

music package

Commodore

Blitz

l/W

Brilliant

£4.99

Basic Intro: 1

D

Fair

£14.95

Cartridges

Super Slot

D

Tiresome

£19.95 each.

Super Lander

RTC

Fair

plus VAT.

Avenger

l/W

Good

Road Race

RTC

Good

Bridge

Vic Invaders

l/W

Avoid

£6.90

Software

Terminal

Panic Driver

RTC

Fair

Software

Line up 4

IG

Brilliant

Abacus

Splotter

O/M

Tiresome

£6.95 each.

Programs

Space Docker

O/M

Fair

or £12.95 for

Guzzler

O/M

Good

two

Defender

l/W

Fair

Petals Around The Rose

L/M

Avoid

Monaco GP

RTC

Bad

Lunar Lander

RTC

Fair

Maze of Death

O/M

Bad

Minefield

O/M

Fair

Bug-Byte

Vicmen

O/M

Brilliant

£7

Another Vic in the wall

B

Good

£7

dK'tronics

Rox

l/W

Good

Deflex

l/W

Tiresome

Tanx

l/W

Unreliable

Space Zap

l/W

Fair

Control

Vicsoft 7 package

Technology

Moroids

RTC

Moronic

£5.95 for

Death Race 2000

RTC

Bad

seven

Mastermind

L/M

Bad

Breakout

B

Avoid

Warlords

B

Avoid

Squash

RTC

Tiresome

Sounds

D

Fair

PR Software

War

l/W

Good

£7.50 for six

Smashout

B

Fair

Blackjack

D

Good

Logic

L/M

Fair

Pickup game

L/M

Poor

Alarm Clock

D

Fair

Notes: In the category column the following abbreviations have been used:

O/M, obstacle or

maze game; B,

break-out type game; RTC,

game with real-time control; l/W, space invaders-

type or war

game; IG, intelligent games; L/M, logic

or mathematical programs;

D, demonstration programs.

■

Visit the Prentice-Hall
computer books displays to
see a wide range of up-to-date
titles at these shops:

LONDON a HOME COUNTIES

Appleby, Myers fr Clarke, WatfO'd

Barbican Business Book Centre, Moorfields

Stanley Botes, Kingston

Brunei University, Uxbridge

Carter & Wheeler, Slough

Dillons, rVWet Street

Foyles, Charing Cross Road

H K Lewis, Cower Street

John Menzies. Old Broad Street

Modern Book Company, Praed Street

Wm Smith. University of Reading

Wm Smith, Reading

University Bookshop, Surrey

University Bookshop, Sussex

Wobsters, Croydon

SOUTH-EAST

Albion, Canterbury

Bowes & Bowes, Southampton

Bowes & Bowes, University of Southampton

Dillons, University of Kent at Canterbury

Robinsons, Bnghion

SOUTH WEST & WALES

Bilbo's Bookshop, Bath

Bowes £f Bowes, University of Bath

Bowes & Bowes, Cardiff

Galloway Bookseller, Aberystwyth

Georges, Bnstoi

Leers. Cardiff

Polytechnic Bookshop. Plymouth

Singleton Bookshop. University of Swansea

Swindon Bookshop, Swindon

Uplands Bookshop. Swansea

University Bookshop, Cardiff

University Bookshop, Exeter

MIDLANDS & EAST

Bleckwells. Oxford

Booktand, Stafford

Bowes & Bowes. Cambridge

Bowes & Bowes, Leicester

Cambridge Computer Store

Dillons, University Bookshop, Nottingham

Heffers, Cambridge

Hudsons, New Street. Birmingham

Hudsons. University of Birmingham

Hudsons. Earl Street Coventry

Hudsons. Hertford Precinct Coventry

Hudsons, Leicester

Hudsons, University of Loughborough

Jarrotds, Norwich

Stsson &■ Parker, Milton Street Nottingham

Sisson & Parker, Wbeelergate, Nottingham

NORTH

Austicks Polytechnic Bookshop. Leeds

Bowes €r Bowes, University of Bradford

Bowes & Bowes, University of Hull

Bowes €r Bowes, Liverpool

Bowes & Bowes, Sheffield University

Briers, Middlesbrough

Browns, Hull

Godfreys, University of York

Godfreys, York

Haigh & Hochtand, University of Manchester

Hudsons, Liverpool

Hudsons, Newcastle

Phillip Son & Nephew. Liverpool

Salfor d University Bookshop

Students Bookshop, Lancaster

Thorn es, Newcastle

W H Willshaw, Manchester

SCOTLAND

Bauermeister, Edinburgh
James G Bisset, High Street. Old Aberdeen
James G Bisset Upper Kirkgate, Aberdeen
John Smith, St Vincent Street. Glasgow
John Smith, University of Glasgow
John Smith. Stirling University Bookshop
James Thia South Bridge, Edinburgh
University Bookshop, Dundee

26 YOUR COMPUTER, JUNE 1982

May-June

Prentice- Hall
computer books event

During May and June new and bestselling computer books published by Prentice-Hall and its
associated imprints — Reston, Reward and Spectrum — will be on display in

bookshops throughout the country.

Featuring — the book you've been wasting for . . .

BASIC
Programming on the

BBC

Microcomputer

Neil Cryer and Pat Cryer

For beginners with no experience of computers, this comprehensive book has
been written with particular reference to the BBC Microcomputer. It provides a
step-by-step course on BASIC and teaches you how to write programs using the
BBC's enhanced version of BASIC. Every program included has been tested on a

production model of the BBC micro. £ 4*xcmxj ty

£5.95 paperback 208 pages 13-066407-3 March 29th C^PUllfls

. . . and many other outstanding titles, such as

Apple BASIC for Business
For the Apple II

£13.45 hardback 400 pages 8359-0228-5
£1 1 .20 paperback 8359-0226-9 1 981

The ATARI Assembler

Don Inman and Kurt Inman

£9.70 paperback 270 pages 8359-0236-6

1981

Prices end publication dsio are correct at the time of going to press
but may be subject to change.

Microcomputer Data
Communication Systems

A Guide to Modems, Terminals, Electronic
Bulletin Boards ... for Users of TRS-80,
Apple II Heath-89 and Other Systems
Frank J. Derfler

£9.70 paperback 128 pages 13-580712-3
April 1982

Prentice/Hall

The PET Personal Computer
for Beginners

Seamus Dunn and Valerie Morgan

£7.50 hardback 240 pages 13-661835-9

£4.95 paperback 13-661827-8 1981

Starting FORTH

Leo Brodie

£14.95 hardback 384 pages 13-842930-8

£1 1 .95 paperback 1 3-842922-7 1 981

International

66Wood Lane End, Heme! Hempstead, Hertfordshire HP24RG, England

YOUR COMPUTER, JUNE 1982 27

Do you find the only drawback
to your Sinclair is that slow,
awkward keyboard? Stephen
Adams examines the solutions
offered by a number of
manufacturers and finds that a
new keyboard could cost you
as little as £20 or as much as
another ZX-81.

The most common complaint about the
ZX-81, or for that matter its predecessor the
ZX-8G, is its keyboard. The keyboard on both
machines is made from three layers of plastic.
The top layer contains the keyboard symbols
on the outside and a metal track on the inside.
This metal track forms one side of a switch.

The bottom layer is the same, but with a
metal track on the inside facing the top layer.
Between these two metal tracks is a plastic
membrane which keeps them separate.
Beneath each key position the membrane has
circular holes though which the top and
bottom metal tracks connect when the top
layer is pressed.

The whole keyboard is only l/8th in. thick
so it can be difficult, without watching the
screen, to tell if you have pushed hard enough
to make contact. As a result users tend to push
far harder than necessary and often for far too
long. The increase in speed that results from
replacing the ZX-81 keyboard with push-
button keys can mean a 50 percent saving on
the time taken to input information.

The keys on the Sinclair keyboard are
arranged in the form of a matrix, with eight
input wires, or address lines, and five output
wires, or keyboard data (KBD) lines. Each
switch is connected to one address line and
one KBD line and when pressed makes con-
tact between them. By checking the KBD lines
affected when an address line is altered, the
ZX-81 can tell which key has been pressed.

Easy to fit

For instance, the shift key will have been
pressed if the address line A8 was affecting
output wire KBDO. Therefore the only wires
that need to be connected to the keyboard are
the eight address wires and the five KBD
lines.

These appear on two sockets mounted inside
the ZX-81, so all that is required is to remove

SURVEY

KEYBOARDS
FOR ZX-81

the plastic tails which connect up the ZX-81
keyboard, and insert the leads from the new
one. There is a hole between the and the 9
key through which the old keyboard tails pass.

As this hole cannot normally be seen, you
must push down on the top of the keyboard in
order to push through the flat ribbon cable.

The best instructions are those supplied
with the Rcdditch keyboard. They contain six
drawings showing how to open the ZX-81,
remove the keyboard tails and attach the new
ones from the keyboard. The Fuller, Redditch
and Computer Keyboards are the only ones
which do not require soldering of the key-
board leads to the ZX-81 even though, as
d*Ktronics point out, little damage can be
done by making a wrong connection.

The other keyboards all require a connection

to the +5V and OV supplies on the ZX-81. A
wrong connection here could cause damage.

There are 40 standard Sinclair keys on the
ZX-81 and although they can have more than
one use, they are all controlled from software,
so only a single-contact push-to-make switch is
required for each key. All of the keys on the
keyboards supplied were designed for this
purpose and you should find no problems in
using them. They have, however, different
key-tops and layouts.

Angle of attack

The Crofton and the Fuller keyboards lay
their keys flat, parallel with the surface on
which they rest, and so are not as easy to use
for someone accustomed to a typewriter. The
rest of the keyboards are tilted to an angle of

28 YOUR COMPUTER, JUNE 1982

HHHHSafBfflfli

30° by cither the case in which they fit or the
stand on which they arc mounted. The
Computer Keyboards keys also rise from one
row to the next giving a better spacing and less
chance of hitting two keys at the same time.
All of the keyboards apart from the Computer
Keyboard — which uses a standard QWERTY
typewriter layout — adopt the Sinclair layout
with extra keys added to each end.

Fuller's extra keys consist of an additional
shift key next to the key making it easy to
press the two keys to give Rubout and " , and
an extra Newline key next to the A key allow-
ing you to press the shift and Newline together
to give Function. As these are in use all the
time, this could prove most useful.

Crofton has provided 1 1 extra keys marked
with Break, Edit etc., to save you hunting for

them. They still have to be used with shift
otherwise they just produce their normal code.
The Crofton and the Computer Keyboards are
the only ones with space bars, but the Crofton
one is rather small.

Additional keys

The Computer Keyboards product has six
spare keys which could be used to duplicate
another key, but because they are the same
type as the rest of the keys they cannot be used
as on/off switches.

The Kayde and d'Ktronics keyboards pro*
vide a repeat key which interrupts the output
lines from the keyboard five times a second.
To the ZX-81, this looks as though you are
pushing the keys on/off very quickly, even
though you have the key down permanently.

This requires components to be mounted on
the keyboard which need a power supply from
the ZX-81.

The cases supplied with the keyboards were
all big enough to hold the ZX-81 printcd-
circuit board. Redditch does not, however,
recommend that this be done with its version.

The ZX-81 fits tightly into the Computer
Keyboards matt-black, aluminium case and a
metal strap is even provided at the back to
hold the 16K RAM pack in position.

The Crofton case does not hold the ZX-81
printed-circuit board at all and it is attached
only to the keyboard. This causes even more
vibration to the 16K RAM pack than usual.
There arc pillars which could have been used
to mount it more firmly, but the holes have
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YOUR COMPUTER, JUNE 1382 29

(continued from previous page)

not been drilled in the case to take the screws.

The Crofton board also supplies a video
amplifier output for a monitor and although it
is good for those who think that a monitor
gives a better picture, it degrades the TV
signal so much that it cannot be used.

The Fuller keyboard's case can be used to
house a complete system which can be
expanded as desired with up to four internal
edge connectors, 64K RAM, power supply
and two 250V mains power-supply sockets for
cassette or TV. All of this is contained in a
14in.-by-8in.-by-3in. injection-moulded plastic
case, which has a LED power indicator. The
only reservations I have are about the edge
connectors, which only allow boards 2in. high
to be connected to them.

The Peter Furlong Workstation is an ABS
plastic shell which will house all the wiring
associated with a ZX-81 and tilt the TV at an
acceptable angle.

The plinth houses the ZX-81 and 16K
RAM pack in a well at the front and the wiring
to the Sinclair disappears through the side of
the plinth to reappear at the back. If you are
still using the original Sinclar leads for the
cassette and TV, then additional holes will
have to be cut at the side.

Crofton

A flat steel box which houses a keyboard, a
video amplifier and the ZX-81. It is of little
use unless you need to operate with a video
monitor and can secure the 16K RAM pack in
some other way. Cost: £42.70 including VAT
and postage.

Kayde

The keyboard is heavy compared with most
and will soon have a case which should prove a
great improvement. The key symbols are
attached with adhesive, and can fall off very
easily. The repeat key is an attraction, but the
instructions for soldering the keyboard cable
need to be clearer. Cost: £27.95 ready-built.

Protos

The Protos system 40-key keyboard is
mounted on a heavy steel plate. The keys have
removable tops, which cover multicoloured
versions of the Sinclair symbols. The green
and brown backgrounds do not make the
symbols easy to see, particularly if you are
colour blind.

The case arrived in seven pieces, six more
than intended, and although it is supposed to
be a heavy-duty keyboard, some of the nylon
pillars had snapped. The keyboard was well
wrapped to protect it from the postman so I
can only assume it was the heavy steel plate
which did the damage.

The ZX-81 must be removed from its case
and placed inside. The edge connector of the
ZX-81 plugs into a suitable connector via
ribbon cable to another printed-circuit board
mounted on the case. This board appears
through the slot at the right-hand side. All the
tape connections are plugged into the ZX-81
via holes at the back. Although it looks
attractive I cannot see this Frome system
working well with the ZX-81 as it is expen-
sive, £67.75 including post and VAT, and
awkward to use.

Computer Keyboards

As the firm's name suggests, the ZX-81 is not
the only computer for which it produces a
keyboard. It is properly tilted, and has a
ZX-81 type QWERTY keyboard with space
bar. Even when not mounted in a case it is at
the correct angle and the stepping of the keys
lends it a professional finish. The connection
to the ZX-81 is via copper-coated strips which
plug into the ZX-81 sockets. The case contains
the ZX-81 and a strap has been provided to
stop RAM wobble. This, in my view, is the
best of the keyboards reviewed, so probably
worth the extra expense. Cost: kit, £28.95;
ready-built, £31.40; case, £15/

Work-station

This is useful when you have to keep all the
cables out of the way, in a position reserved for
the ZX-81. The TV might prove too near the
eyes for some, and the Sinclair printer needs to
have modifications made to the plinth. Cost:
£18; power switch, £3; cassette change-over
switch, £3.50; aluminium floor, £4, All prices
include VAT and postage.

Fuller FD System

The keyboard for this system provides a cheap
start to forming a quite comprehensive layout
for the ZX-81. The keyboard is not the best
available, but it has some useful facilities. I
would recommend this as a portable system
for demonstration use, as all the equipment
required, apart from the TV and cassette
recorder, can be packed in one case. Cost; kit,
£19.75; ready-built j £25.75 for the plain
40-key version; £35.45 for the 42-key version
in the case; £43.45 for a ready-built model;
motherboard with two edge connectors,
£16.75; three edge connectors, £21.75; four
edge connectors, £26 -75, all of which are
ready-built; 64K RAM Pack, £45; 16K
version which can be upgraded to the 64K
version, £35.95; both are ready-built; 9V
power-supply unit, £6.75; 12/5V for £13.95.
Various other switches and sockets are
available. There have been reports of consider-
able delays in delivering this keyboard so,
before ordering it, it is worth ensuring that
you have written confirmation of an acceptable
delivery time.

Clockwise from top; Dean Electronics Computer Keyboard; Fuller FD System; Redditch;
d'Ktronics; Kayde; and Crofton Adaptakit Centre; Peter Furlong Workstation,

d'Ktronics

A pleasant keyboard, mounted at the correct
angle, with repeat facility. The instructions
are clear with a section on faults that can
occur. The keyboard has to be soldered to the
ZX-81. A numeric pad can be connected next
to the keyboard on the right as shown in the
accompanying photograph. Cost: £27.95;
numeric keypad, £10.

Redditch

An easy-to-use 40-key keyboard, less expensive
than most, but requiring a case to make it tilt
to the correct angle. The connection to the
ZX-81 is via two plugs, and very clear, simple
diagrams make it easy for those concerned
about harming the computer. Cost: kit,
£20.50; ready-built, £27.75; £10.30 for the
case.

ADDRESSES

Suppliers

Crofton Electronics Ltd: 35 Grosvenor Road,
Twickenham, Middlesex TW1 4 AD. Tele-
phone: 01-891 1923/1513.

Kayde Electronics Systems: 48/49 Exmouth
Road, Great Yarmouth, Norfolk NR30
3DP. Telephone: 0493-55253.

Redditch Electronics: 21 Ferney Hil! Avenue,
Redditch, Worcestershire B97 4RU. Tele-
phone: 0527-61240.

d'Ktronics: 23 Sussex Road, Gorleston, Great

Yarmouth, Norfolk. Telephone: 0493-
602453.

Computer Keyboards; Glendale Park, Fern-
bank Road, Ascot, Berkshire. Telephone:
0347-4731 .

Peter Furlong Products: Unit 4, South Coast
Road Trading Estate, Peacehaven, Sussex.

Fuller Micro Systems: The ZX Computer
Centre, Sweeting Street, Liverpool 2. Tele-
phone orders: 051-236 6109.

Frome Computing: 20 Ashtree Road, Frome,
Somerset BA11 2SF, Telephone; 0373-
71435. ■

30 YOUR COMPUTER, JUNE 1982

If you Ye looking for a home computer, you 11 already
know that the VIC does it all. To help you get started,
we have put together this attractive cost -saving
package

hip on Co|our

V I U " £U computer

+ Cassette Deck
4-10 Blank Cassettes
Introduction to Basic
Parti
+ User Manual

3C j£? ^ET jST 2* 4£4k fi

** #> «: i*< ^ ^ v f# fp; r

~^ & AF && £& &/ /S& S> :j£/ ;£/ £2S£ ££? &U

r™3

price plus VAT £243.80)

ft$ Dot Matrix Printer Memory Expansion Board Plug-in Memory Expansion

*aO^\«^ V <S t ♦ i ^ on Multi-slot unit used to Cartridges

>*"^lU *^° cSeSD' e Minea.30 aCCep,memO,yand/Or 3k - £26.04, 8K- £39.09,

**^\^\& ^v^ ffiSE JESf 9ame and program 16k - £65.17 plus VAT

-%a^*lo*^ *** rt \# characters/seconds, rnnridnw *- • n ^ »*-...,*

^*2a*^ »^ I «** £1W96 p |us vat SvSRrt vat s,lifl,e Wve Flopw D,sk Uilit

^vv^^^^ p £395 - 00 p |us VAT

k^S^* \^^ The standard features of * he Vic are: * 5K RAM expandable to 32K • 16 screen

o^ V ^&$$& colours * 8 character colours * 3 tone generators, each of 3 octaves - plus white

W* tfo*^& no ' se 9 enerator * Screen display 22 charactersx23 lines deep • Full PET type

* v graphics • High resolution graphics capability • 8 programmable special functions.

Goods reqwred Pnce MAIL ORDER to: Adda Home Computers Ltd \#

FREEPQST, London W3 &BR or tefcpnor* your w

. order (24 hours a day) to 01 -992 9904 quoting your

Visa. Access or American Express number.

^ — ^— — t ( enc(0SJJ a ^^ ma(ie payable | a^ Home Computers

— — Limited tor

£ _

~~ * Please charge my Visa/Access/American Express account. My acount

Add £4,00 post pacfcng and »n$uranee for Total £ ngffibef te

special deal and £1 .00 post, packing and * please add my name to your mailing list

insurance for an other items. Add 15% to ail • Delete as applicable

prices for VAT

Date ^ ^%^

Name: SHOP ADDRESS: Adda Heme Computers Ltd, A J^ % J^ *

154 Victoria Road. Acton. London. W3. ^^k / ^k /^^

Artj -.„ c __ (near North Acton tube station) y^k & ^k ^^^*

AflflfeSS " Ttf 01-992 9904 ,.. A ^m W W

OPEN: t0am-6pm (Tuesday-Friday), /l* m ^^^^^

' ~ 10am-5pm (Saturday) . f J^l^^J^

TERMS AND CONDITIONS: All goods sold subject to Adda terms and conditions of sale, full details avafcbfc on request, bat ^*^& m^^^^

include: 7 day money bach guarantee. Adda 12-momh hardware warranty. Please allow 21 days lor detatry. Allow 7 days for ^^^F^* ^^^*

personal cheques to be deared. Quoted pnees are exclusive of VAT. ^^^^^*r ^m

YOUR COMPUTER, JUNE 1982 31

Sleeve notes

■Although the flexi- record is a new way of
distributing software, you should remember
at all times that the fundamental principle
involved is the same as when a program is
stored on tape. That is, the electronic
binary signals are enshrined in a physical
form to be replayed at a later date. It makes
no difference to the computer what medium
the signals are stored on when it receives
them.

■With this in mind, there are two ways you
could load your flexisoft disc. The first is to
record the disc on to tape, and use the tape
just like any other ZX tape. The second
method is to load directly from the record
player. The first method is best for most
people as it requires little or no change in
the ordinary tape-loading procedure.
Though you will have to experiment with
the recording levels as you would with any
commercial cassette.

■The best setting on an ordinary music
centre is treble zero. If you have to move it,

. move it up, bass zero, though if you move
the bass, move it down — but not too far. \
did not use Dolby when recording the disc,
but if you do, ensure that Dolby is on when

ALL IN THE

This month's Your Computer
cover could reduce the cost of
recorded software from pounds
to pennies. That thin slice of
plastic will cause tremors in the
software industry. Bill Bennett
explains how we put Othello
on a flexidisc.

ABOUT 16 MONTHS 1 talk of distributing soft-
ware commercially by the new and revolut-
ionary method of putting programs on a flex-
ible disc was temporarily shelved when it was
discovered that the then most popular
machine, the Pet, did not lend itself readily to
the idea.
Then the Sinclair ZX-80 and 81 arrived on

the scene. These machines totally changed the
face of microcomputing and at the same time
transformed the software market. At more or
less the same moment as the launch of the
Sinclair ZX-81 Your Computer appeared on
the book-stands, a computer magazine which
has always thrived on the volume and quality
of correspondence from its readers.

One morning I came across a letter in the
Your Computer post from Bernard Beeston.
He suggested putting some ZX-81 software on
to one of "those flexi-rccord things**. At first I
just filed the letter for reply. That night I
thought about it again and in the morning dis-
cussed it with my colleagues.

In short, it was a brilliant idea. Bernard
Beeston is a collector of free flexidiscs and on
seeing the Tomorrow's World television trans-

you load the tape, f turned the left channel
right down, and set the level of the right-
hand channel to zero dB using a level
meter. If you do not have any meters, you
will have to judge the correct volume either
by ear, or by guesswork. It is a matter of
courtesy not to play the record too loud as
it makes a real din.

I Loading the program directly from the
record player should be fine. However you
will have to watch that you do not damage
your computer. This is easily done if too
high a volume is put into the machine. If
your record player has a headphone socket
or an earphone socket use it. The software
does load, although sometimes minor
mistakes occur as information is misread.
Because of that we reproduce the program
listing here for anyone who experiences
this problem.

I Remember the program is for an expanded
ZX. It will definitely work with the 16K
RAM pack and it should be possible to run
on an 8K ZX-81 . It loaded into a 3K ZX-81 ,
but left no space for the variables.

A roll of black vinyl feeds into the press to be stamped with the program cut into squares and stacked.

Othello program listing

t®*EM GTHELLG2 INTERFACE DEC
Si PI 3 AMENDED BY ROY EASTWOOD
10 FAST

20 REM INITIALIZE ARRAYS
36 DIM B$<2,2>
40 DIM C$<2,2>
5@ DIM A*<2,200>
60 REM DRAW BOARD
70 LET Ft*
80 LET G*^ J
90 LET K*=*
180 LET m=*
110 LET J*="B2 3456739 ■
120 LET A$vi> =H$+'i"+F$+' l B"
+6*+" ■ "+Ff+" ■ "+G$+ M « I, +F
jr-r" M "+G$*" m "+Fft" ■ "*G*+

130 LET A*<2> -W+^lK+F^-lK"
+G*+"2 B 3 ,, +F*+"3 ■ 4"+GS+"4 BS"

+ "SB a +K*
140 LET fitC 1, 39 TO 92> = '
150 LET R*<2,89 TO 92>='
168 LET fi*< 1,169 TO I 12)='
170 LET Af<2,109 TO 112>=°>
130 LET D$="BCDLNVWX"
190 LET H*="B FAST THEN WASN TTol
STOP SON (7FQ_ STEP RTN ^IHJ \X2
SIN LPRINT&^glLLI ST LN Tarter

EJ/AL ESfces BUN **efeEQ:HR* or

Hi

Osgr E£t not usr (122 SLOW [0 TO

C*$TRrJ3 nND 0'
200 PRINT AT 1,6,
210 FOR A=l TO 161 STEP 20
220 ^OR D*A TO R+19
230 PRINT A*<i,D>;
240 NEXT D
250 PRINT TAB 6,
Z€0 FOR D^ft TO fl+19
270 PRINT fi*<2,B>;
280 NEXT D
290 PRINT TAB 6;
380 NEXT A

310 PRINT AT 8*8; "HE ff 1 ; TAB 26;
•*V0U:«» ",TAB 3;"M';TflB 30; ■ ■"
330 SLOW

340 REM DECIDE WHO IS TO MOVE
350 IF RNBX5 THEN GOTO &S0
360 REM COMPUTERS MOVE
370 LET B*<l>-" — "
380 LET B*<2>= M " M
390 LET CS<1 >="■■'
400 LET Cf(2) = 'M'
402 PRINT AT 21*0; "

410 FOR K=l TO 60
420 LET B=CODE E*<K> -140
430 IF A* <1,2*BX>'W AND fi*(l,
2*BK>'W THEN GOTO 650
44© LET H=0

32 YOUR COMPUTER, JUNE 1382

GROOVE

mission of the ZX program, he hit on the idea
of putting ZX software on flexible records*

Not long after receiving the letter from
Bccston, another event occurred which pushed
the idea further forward. I discovered that the
signals used by the Sinclair computers to store
information on tape were not only in the audio
range, but exceptionally well suited to record-
ing on flexidisc. We simply had to go ahead
and test the idea.

Simple method

The ZX-81 - and for that matter the ZX-80
— uses a particularly simple method of storing
information on cassette. The zeros and ones
that make up the binary codes used by the
computer are stored as simple sine waves. A
zero is represented by a sine wave of a given

number of cycles; a one is stored as a wave of
another number of cycles. Between the indivi-
dual bits is a short blank, which is about as
long as the one-bit sine wave in time.

This information is stored serially on a
cassette, and is loaded simply and relatively
quickly into the memory of the micro at 300
baud. The signals are recorded on ordinary
cassette tape, in exactly the same way as a
musical signal would be. This is very helpful
because in the same way that, for example, a
pop group would record their music initially
on tape before transferring it to disc, the
ZX-81 software can be transferred from
cassette to disc.

In fact, the practice is somewhat more com-
plicated than the theory, as I discovered when
I went along to the cutting studios. The studio

The squares are trimmed into discs and the Your Computer labels are then printed directly on to them.

450 FOR X=l TO 8

460 LET H=CQBE Df <X> -50

470 LET E=0

488 LET F=B

490 IF ASCI, >;F+N>*2> OB*a,2) T-
HEN GOTO 530

509 LET E=l

516 LET F*F+N

520 GOTO 490

530 IF fi*a,<F+N>:*2> OC*a,2>0
R E=0 THEN GOTO 630

540 FOR fl=B*2 TO F*2 STEP N*2

558 LET fi$(l,fi-l TO fl> ^CS<1)

5€8 LET LINE=1+2*IHT <<A-i>/20>

570 LET CQL=4+fl-20*INT <<A-i;/20>

5S0 PRINT HT LINE, C0L;C$Ci>

590 LET fi*<2,A-I TO fi> «C$ C2>

600 PRINT fiT LINE+1, C0L;C*<2>

610 LET H=l

620 NEXT fl

630 NEXT X

S48 IF B$<1> -'fT 1 OR H»l THEN GOTO
660

650 NEXT K

660 IF B*<I> ="TT THEN GOTO 3?£

6?e IF H-0 THEN GOTO 780

SBB REN HUMANS MOVE

690 LET £$a>="ff'

760 LET B$<2>='li"

710 LET C*U>*" "

720 LET C$C2>="" M

722 PRINT RT 21,6; "ENTER MOVE E-G-
19 (0 FOR SCORE)"

730 INPUT B

740 IF B-0 THEN GOTO 780

750 IF ft$<i,B*2X> ,, S" RND fl*U,B*2>
OV THEN GOSUB 1010

760 GOTO 440

770 REM CRLCULflTE SCORE

?m LET CF-0

790 LET HP=CP

806 FOR fi=23 TO 177 STEP 2

310 IF R*<I,R>* "■*' THEN LET CP*CP+1

320 IF fl*<!,fi>* "■" THEN LET HP=HP+1

330 NEXT Fl

340 PRINT «T 10,0;CP;TRB 27; HP

350 IF CP+HPC64 THEN GOTO 690

860 IF GP>HP THEN P RINT RT 21,0; M

nrRTNi

870 IF CPOfF THEN PRI NT RT 21,0;"
[VOU MINI

380 IF CP=HP THEN PRINT RT 21,0;"
lDFRMj

390 STOP

1000 REM INVALID HOVE
1010 PRINT RT 13,0, "CHERT* N ;TRB O;
"IF VOU*,TRB 0; M DO IT"; TRB 0;"
RGRIN": TRB 0;"I WONT"; TRB 0; u PLRY"
1020 LET B=0
1030 RETURN

where we made the initial software record
looked like the bridge of the Starship Enter-
prise. Around the side of the room were all
kinds of cassette players, recorders and
amplifiers. In ihc middle was a desk, covered
with mixers and various pieces of noise-
reduction equipment.

Among the hyper-modern hardware was an
apparatus which resembled a microcomputer
— in fact it was an audio analyser, which pro-
jects a display of the audio spectrum on a
screen. Each frequency band within that
spectrum is represented by a vertical bar,
which waxes and wanes with the quantity of
that frequency present in the sound.

Like dancing spirographs

In addition a cathode-ray tube display
showed Lissajous figures. These are rather
interesting displays which show the relation
between two harmonically varying signals.
They look rather like dancing spirograph
drawings. All this equipment was very impres-
sive but it was there for a reason: it told us that
superimposed on the ZX-8Ts output signal
were a number of other signals.

These signals normally do not make any
difference to the loading of programs on the
ZX-81 as there is a very wide tolerance. How-
ever, with the recording of software on to disc,
we were entering unexplored territory and had
to be careful.

The computer signal sits somewhere in the
ordinary audio spectrum, at around 3kHz to
4kHz. Being a sine wave, it should not have
any other frequency components- The sine
wave, if pure, does not contain any other
components because it is the fundamental
component itself. If it is amplified too much,
the peaks are clipped and the wave begins to
look like a square wave — which, incidentally,
is how a guitar fuzz-box works.

The reason this is important to micro-
computers is that when a sine wave is distorted
into a square wave, other frequency com-
ponents are introduced which confiuse the
computer. This is what sometimes happens
when a ZX program is Saved or Loaded too
loudly.

There were two main sources of sound
present on the master tape of the text program,
other than the computer signal wanted. This
master tape was made by recording directly
from the program cassette to a reel-to-reel tape
recorder. These sources of extraneous sound
are referred to as "noise" by audio engineers.

Two types of noise

The original flexidisc test tape had two types
of noise on it. Later, I discovered that more or
less all Sinclair tapes have these types of noise
because of certain factors associated with low-
cost tape recorders, and we all know that the
chaper tape recorders work best with the
Sinclair.

The first type of noise was the background
noise of the cassette itself. I do not want to
become too involved with the technicalities,
but cheap, standard, cassette tape has a back-
ground hiss, which is mainly at the higher end
of the audio spectrum.

The other noise was one picked up from the

recorder itself, probably due to the motor.

(continued on next page)

YOUR COMPUTER. JUNE 1982 33

(continued from previous page)

Another source of noise is the stretching of the
tape and a fourth could be due to mechanical
imperfections on the cassette itself.

The random-noise part of the signal — that
is, the background hiss — was reduced by a
Dolby system. The lower tones associated
with the tape drive were harder to eliminate,
but the worst of it was removed by a graphic
equaliser. The original test tape was recorded
in stereo, but the flexi-record you will have
received with this copy of Your Computer was
recorded in mono.

This treated signal was then stored on a
length of open-reel tape. The beginning of the
program and the end were marked on the tape
by cutting it at the relevant point and then
inserting a short stretch of yellow tape. The
whole was then reloaded on to the tape deck
ready to cut the disc.

Disc-cutting machine

The disc-cutting machine looks just like a
record player — one of the very expensive
stereo variety. Yet> unlike the machine that it
so closely resembles, it does not play records
but cuts them. This is done by making the
stylus vibrate in the disc material as it tracks
towards the centre of the disc. The process is
just like playing records, but in reverse.

The material that the disc is cut into is called
an acetate. It looks just like an ordinary black
12in. record, except it has neither label nor
groove — at least to begin with. The turntable
is rotated at the set speed, with the acetate
firmly clamped to it. The initial "run-in"
groove is cut, and the turntable stops. Then
the tape machine is cued to the beginning of
the software. At the same moment as the tape
machine begins to play, the record cutting
starts automatically.

It is possible to set an adjustment that
governs the pitch of the grooves, that is the
amount of material that is left between the
gaps. Ordinarily the more of this, the better
the quality of the recording. This is because
the stored sounds of one groove can impose
themselves on another if the walls between
them are not sufficiently wide. Of course, the
optimal setting of this adjustment is one which
utilises all the available material between the
edge of the record and the point where the
stylus picks up.

The acetate platter which has the record cut
into it is 12in. across, but the record is only the
7in. in the middle. Once the acetate is cut, a
label is stuck on the middle, and the acetate
disc can be played just like an ordinary record.
To test the process, this is just what I did.

I decided the best thing to do would be to
tape the program on the disc and play it just

Under the microscope a series of short white fines and spaces show up in the grooves. This is the
form in which the binary digits are encoded on the f/exidisc.

like an ordinary piece of software. I made a
number of different recordings, some in
stereo, some in mono, some with treble turned
full on and some with the settings all at zero.
The software loaded, but not when it was
recorded in stereo; the flexidisc you have is in
mono.

The master, which is another name for the
acetate disc, for the Your Computer flexidisc
was cut at Pye recording studios in London
between takes of the new Tight-Fit record.
Most of the pop stars wandering in and out of
the studio would probably have covered their
cars in disgust if they heard the disc. Listen for
yourself and hear what it sounds like,
However, to the cars of Tony Bridge, the
engineer who cut the disc, the sound was
music because he is a ZX-81 user. It was very
useful having someone who understood com-
puters working on the disc,

Once the master disc is cut it is plated in
metal. The metal plates are then pulled away
and become the stampers that are used in the
flexi-record factory. The flexi-record factory at
Charlton, south-east London, turns out

How to play Othello

Othello, which was originally called Reversi, is a board-game for two players, played on a
conventional chessboard with eight-by-eight squares. The pieces are double-sided, coloured black
on one side and white on the other. Any of the opponent's pieces in a straight line between the
last piece played and another of the player's pieces is "captured", that is to say turned over, to
convert it to the player's colour. The game finishes when the board is covered with pieces or when
neither player can move, and the winner is the player with the most pieces at that stage.

If the program has loaded correctly then a grid of eight-by-eight squares will appear, just like a
chessboard. Along the top will be the numbers from two to nine and down the side one to eight.
There are two possible states at the beginning, either it is your go first or the computer's. If it is
your go first the computer will prompt you with the message: "Enter Move EG 19 (0 for score)". If
the computer is to move first the screen will be dark for a while.

When moving remember to enter the ROW first followed by the column number. Sometimes
you can cheat and get away with it. Be warned, if you do the game will finish. Entering a zero will
give you the score, do this at the end of the game.

records by the hundreds, usually of pop
music, or maybe an advertising message. They
have even made records for use in by-election
campaigns,

The process used to make the records was
explained to me by managing director John
Moon, One of the most important features of
producing flexi-records is the vinyl on to
which the discs are stamped. This is available
in a number of different thicknesses and
colours — it can even be metallic gold or
silver. Black is, however, the usual choice
because it looks like ordinary records.

A special design

The vinyl is held in huge reels which are
mounted on an axle behind the flexi-record
press. The press is of a special design, built
and designed by the directors of Flexi-records
themselves.

Normally the stampers push out four discs
at a time. The key to making good flexi-records
is the hole in the middle, which is punched out
at the same time as the actual stamping. The
records are then cut, and stacked on a spike. At
this point the records are still square.

They are loaded, a bundle at a time, on to a
cutter, which works in the same w*ay as a
pastry cutter. The last stage in the process is
when the labels are printed directly on to the
flexi-record. This is done with a Heidelberg
printer, which is a pleasure to watch.

Of course, a large sample of the flexidiscs
were tested, and they all worked. So all that
remained for us to do was to put the discs into
the magazine and distribute them throughout
the country. I hope you manage to beat the
computer at Othello or Reversi. 9

34 YOUR COMPUTER. JUNE 1982

MQZOGS

IHL-UbO is a brand new
Same for the 16K ZX81 1 unlike any
other game you Ve seen on the ZX81 . This is without doubt
the best same available for this computer, and if you don't believe us, ask
somebody who has seen it, or go down to your local computer shop and ask for a
demonstration.

MAZOGS is a maze adventure same with very fast-moving animated graphics. A
large proportion of the prosram is written in machine code to achieve the most
amazins sraphics you have ever seen on the ZX81 .

You will be confronted by a large and complex Maze, which contains
somewhere within it a glittering and fabulous Treasure. You not only have the
problem of finding the treasure and bringing it out of the maze, you must also face
the guardians of the maze in the form of a force of fearful Mazogs. Even if you
survive their attacks you could still starve to death if you get hopelessly lost.
Fortunately, there are various ways in which you can get help on this dangerous
mission.

There are three levels of difficulty, and the game comes complete with
comprehensive instructions. The cassette on which the game is supplied is of the
highest quality, and loading is guaranteed.

Mazogs is available from Bug-Byte and most good computer shops at £10.00
inclusive.

AMAZE

ADVENTURE

GAME

FOR

iind
ZX8I

100 The Albany, Old Hall Street, Liverpool L3 9EP

Please servo" me

Qty

Hem

Price

8u3-6yte ' MAZOGS " Cassette
For £10.00 inclusive

t enclose cheque/P.O
OR Please debit my:

A«ess <«~rrnrrrmrnr

Barcfaycard

4949

Expiry Date.
Name

Address.

Dealers Discounts
Available.

ACCESS/BARCUWCARD
ORDERS WELCOME ON \
24-HOUR ANSA PHONE
051-227 2642

-Code.

YC-6-82,

YOUR COMPUTER, JUNE 1382 36

INTERVIEW

ADDED EXTRA FOR

Ron Bissell has been
in on the explosion in
microcomputers from
the start. With fellow
director Ken
MacDonald he has
built Macronics up
into one of the major
ZX soft- and hardware
houses. He talks to
Brendon Gore.

Ron bissell first came into contact
with computers while in the sixth
form. A trip to Wolverhampton
Polytechnic introduced him to an
early U.S. computer.

"We were allowed to write pro-
grams for it, punched on paper
tape", says Bissell. "It was a whole
wall full of entertainment with flash-
ing neon lights and chattering
relays".

After leaving school, Ron Bissell
went to Queen Elizabeth College,
London in 1962 to do a general-
science degree. Unfortunately, he
failed his first-year exams, which he
attributes to the disruptions caused
by leaving home, moving to London
and trying to settle down to college
life.

Nothing daunted, he found him*
self a job in the electronics industry
with Contactor Switchgear (Elect-
ronics) Ltd. He worked in the
company's development laboratory
building prototype timers, logic
circuits and remote-control TV units
from schematics. It was very useful
experience, he says with just a touch
of understatement.

After a year in industry, he sat his
first-year exams at Chelsea Town
Hall. He remembers it as being sur-
prisingly easy, a pleasant week with
beautiful weather. He was a little
surprised when he passed, as he was
weak in mathematics. But he drew
small sketch graphs in answer to
most of the questions, and thinks
that they must have done the trick.

Having graduated, Bissell started
working for British Steel, He was
assigned to work with the O/M
(Operations and Methods) depart-
ment on the problem of cutting up
steel bars into precise lengths with
minimum wastage. He looked at a
Fortran program the O/M depart-
ment had written to solve the
problem, and decided that Fortran

was not that difficult a language to
learn.

A year after joining British Steel,,
Ron Bissell left the company to join
the West Midlands Regional Health
Authority, Officially he was part of
an O/M department, but within
months he was put into the O/R
(Operational Research) division.
This entailed considerable work
with computers.

"I was involved with the setting
up of an emergency bed bureau in
east Birmingham", says Bissell.
"The idea was to stop some hospitals
from being swamped with patients
while other hospitals had empty
beds.

"We had to produce computer
forecasts of the likely number of
patients expected on any particular
day of the year. By combining the
seasonal and weekly patterns of
admissions, we were able to produce
a table of the likely number of
patients to be admitted to hospital in

the West Midlands on any day of the
year".

The origins of Macronics lie in the
West Midlands Regional Health
Authority. Ron Bissell, Ken
MacDonald and John Kwok all
worked for the WMRHA, and they
were all quick 10 spot the potential of
microcomputers. In 1979 the three
of them decided to try and design a

'Memory-mapping

ZX screens was

thought

impossible 9

cheap alternative to the semi-profes-
sional machines they had been work-
ing with. However, it became the
computer that never was.

"We made the decision to abandon
our computer after Sinclair launched
his ZX-80", says Bissell dryly. "We
had been aiming to produce a micro-
computer for around £150, which
was twice the price of the ZX-80.

"In some ways our machine would
have been very similar to the ZX-80.
It would have had a touch-sensitive
keyboard and single-key instructions
— John Kwok was very keen on
single-key instructions after seeing
them used on a Wang machine. It
would have had a 32-character
screen, but we were going to make it
32 square rather than 32 by 24".

Faced with the choice of producing

N

a comparable machine to the ZX-80,
but at twice the price, they decided
to drop it and concentrate on pro-
ducing software for the ZX-80;
"There were so many limitations in
the ZX-80 that there was obviously a
need for programs to get round
them".

Ron Bissell's first program for the
ZX-80 was a memory-map screen
display, "Everyone had been saying
you could not memory-map the
Sinclair screen", explains Bissell.
"In fact it was simply a matter of
setting it up with blanks on all sides
and knowing where it was in
memory. This allowed you to Poke
to any pan of the screen that you
wanted, which in turn meant that
you could run the kind of games pro-
grams that everyone else was
running on other machines".

The memory-map program sold
for around £1 a listing, says Bissell.
For the first six months they sold
around 30 listings a week, which was
not bad for the first program. But
they did have the advantage of not
having any competition.

John Kwok had dropped out of the
team by this point. "He was more
interested in the concept than the
actuality", says Bissell. "Besides, he
had been made head of the authority's
microcomputing development project
and he was putting his main efforts
into that".

A natural division of responsib-
ilities evolved between the remain-
ing partners. Ken MacDonald
looked after the marketing and
financial side of Macronics while
Ron Bissell took charge of the tech-
nical and software side.

The next Macronics program to
hit the market was the active-display
program. This was designed to get
round the fact that the ZX-80 screen
was static, so that nothing happened
unless a key was depressed. But, by
this time the competition was start-
ing to arrive.

"We got our active-display
program out at about the same time
as Ian Logan produced his version",
says Bissell. "The difference
between the programs was that his
version involved copying whole
sections of the Sinclair ROM into
memory. That worked well, but it
used up a good deal of memory. In
our version, we copied the necessary
parts of the Sinclair ROM into our
program, but without the extras.
This meant it needed very little
memory. There was some screen

36 YOUR COMPUTER, JUNE 1382

ZX-81

flicker between displays, but at lea$t
they would change and update by
themselves".

This program went on sale for
about £5. It was part of Macronics
strategy to sell techniques as well as
games, playing on the "look what
you can do with your ZX-80 that no-
body else can" idea.

The price of the program was
something Macronics had learnt
through experience. "£5 or £6 was
the optimum price for a program",
says Bissell, "and it still is. You
cannot sell anything for much less
because people will think it is
rubbish, and you cannot sell any-

'Our micro was
to be similar
to the ZX-80'

thing for much more because people
do not have the money. It docs not
really matter what is in the program
— that is the price for it".

Macronics sold a number of copies
of the active-display program, but
they were a little disappointed that
sales were not higher.

"We do not seem to be reaching
the market for some reason. I
remember estimating once that we
were reaching, at a maximum, two
percent of the total number of
Sinclair users, which seemed an
abysmally low figure".

One possible reason for this lack of
early success was the Macronics
policy of selling listings rather than
cassettes. Bissell and MacDonald felt
that listings were cheaper to produce
than cassettes and avoided loading
problems.

"We did not discover we were
wrong in this until we went to a
micro show in September 198L All
the people there were asking for
cassettes. Purely for psychological
reasons, people would rather buy
something they could use directly.
Through mail order you could sell
listings reasonably well, but at shows
there was just no way".

Macronics was also writing soft*
ware for the ZX-81. The first four
programs included Dragon Maze
and Planetoids. They were con-
ventional Basic programs with little
machine code.

"The only machine code I wrote
then was a reverse-scroll routine

which scrolled down the screen
rather than up", says Bissetl.
"There arc problems with the
Sinclair scroll in that it changes the
length of lines at the bottom of the
screen. If you have an array memory
which falls above the display file,
every time you add something to the
bottom line of the screen the whole
array memory has to shunt up which
takes forever.

"This means you cannot do any
fast graphics programs while you
have a large amount of data in the
variable area. To overcome that I
had to wTitc a machine-code routine
which did the scrolling but kept the
screen its normal size so that nothing
was moved around".

But the software market for the
ZX-81 seemed less attractive than it
had been for the ZX-80: "We saw-
that there was not much we could do
in the way of software that other
people could not do equally as well.
So we looked at what was coming
next, which was hardware".

Macronics first hardware project
involved a printer interface. Ron
Bissell built a £199 Seiko printer and
interfaced it to the ZX-81. The

printer interface went on display at
another micro show, but although
there was some interest in it he has
decided to shelve the project for the
rime being.

"It soon became obvious that the
main interest was going to be in an
alternative storage method",
explains Bissell. "People were pro-
ducing enormous programs that took
the best pan of 15 minutes to load,

'Storage media
were clearly of
major interest'

with no guarantee that they would
load, so a different system of storage
seemed the thing to concentrate on".

The result was Fiz, which is not a
new type of cola but a Floppy Inter-
face for the ZX-81. Fiz consists of a
disc drive, power supply and mother-
board. The motherboard is fitted
with edge connector slots so that the
system can be expanded.

"There is a slot in the mother-

board for plugging in the ZX-81 pro-
cessor card, but this entails an
external keyboard with the usual
external leads", says Bissell. "Many
users have external keyboards and
that is the best way of doing things.

"The RAM pack also plugs on to
the motherboard, but there is no
need to use a RAM pack bigger than
I6K. Other slots are available for a
printer intefaee, disc interface, net-
work interface and a high resolution
VDU card".

With the Fiz costing £259 plus
VAT, it is possible to buy a complete
disc system for less than £350. Ron
Bissell admits that no one is likely to
buy his disc system from scratch, but
he thinks there is a market among
schools and small businesses that
have already bought a ZX-81.

"If you are buying a disc system as
a disc system, the last thing you
would buy is a ZX-81. You would
buy something like a Zerox. But if
you already have a ZX-81 and have
bought £400 worth of hardware and
programs, as many people have
done, then you do not want to let go
of it. That is the demand wc arc
supplying."

YOUR COMPUTER, JUNE 1982 37

Support for ATOM and ZX

The Atom Magic Book

A wealth of games and other programs: ttoring speech in your ATOM,
converting programs written in other BASICs tape recording hints,
and many more useful software and hardware rips. £5.60

Getting Acquainted with your
Acorn Atom

By Tim Hartnell and Trevor Sharpies .80 programs including
Draughts 1

£7.96

The Memory for your ATOM

16or32K BYTE VERSIONS Expand your ATOM to 28 or 38K RAM

Ideal for Word Processing, Chess programs and Business Software.

Fully Compatible with other Acorn ATOM software and hardware

Versions available to fit inside the ATOM while still leaving room
for other extensions such as the Acorn ATOM colour encoder board.
Eurocard rack mounting types also available

PRICES; INCLUDING U.K. P&P &15% VAT

MZ163A 16K Built & tested to fit inside ATOM'S case £59.50

MZT03B 32K „ „ .... £74.00

MZ163C 16K Built & tested, Eurocard rack mounting £62.00

MZ163D 32K „ ., „ „ £7650

MZ163E Bare PCB to build any of above with data £23.00
MP 100 DC/DC converter; powers any MZ163 board from

unregulated 8V luppJy such as the ATOM mains adaptor £8 SO

S.A.E. for further details.

VISA

ALL PRICES INCLUDE U.K. P&P
♦ 15% VAT WHERE APPLICABLE.
OVERSEAS CUSTOMERS ADD
£1.50 CARRIAGE PER ORDER
PAYMENT WITH ORDER PLEASE.

TIMEDATA LTD, Dept A , 57 Swallowdale, Basildon.
Essex. SS16 5JG Tel; (0268 M11 125 (MON-FRl)

The Explorer's Guide to the ZX81

IF YOU'VE GOT A ZX81 THEN YOU NEED THIS BOOK*
Programs f or 1 K RAM, and programs for 16K RAM.
Games, Business and Engineering Applications.
RAM 6c 1/0 Circuits. Useful ROM Routines. Hints
and Tips. 120 pages

£4.95

What Can I Do with 1K?

By Roger Valentine. A fresh and original book
containing 40 programs and routines for the
unexpended ZX81.

34 Amazing Games for the 1KZX81

by Alastair Gourlay.

£3 .95 1

The ZX80 Magic Book

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ZX 80/81

MATHEMATICAL PROGRAMS

Add real power m Advanced Mathematics to your Sinclair computer (ZX81 16K RAM
and ZX80 with 8K ROM).

C ALCU LEX II General Mathematical Program Turns the 2X81 into an effective tool
for advanced Algebra, Differential C$*cukis and Integral Ca cuius. On the Moving
Graph you can watch the computer plotting Quadratic, cubicv and higher equations,
finding the roots, solving multiple simultaneous equations. You can inspect changing
values of the definite integral in the Integra Calculus wd, at the press of a key, get
the value of the differential for any value of an equation (however comiicatedl in the
Differential Calculus. Introduces you to DouWe Integration, to Harmonic Analysis and
the use of Polar Co-ordinates. Solves problems that cannot be solved by standard
formulas m algebra or the integral calculus.

CALCULFX HI Further Mathematics (Vectors) This combines vector algebra with
the graphic display of the addition and multiplication of two-dimensional vectors, a
revolutionary graphic treatment of three-dimensional vectors (using unit vectors),
illustrates the formation of vector equations and al-ows input and graphic display of
equations with complicated functions of the independent variable At the same time
as it plots vectors and vector equations, it prints out the values of vector sums.
Cartesian co-ordinates, direction cosines and angles. Can be used to calculate scalar
and cross-products, both direct and using unit vectors- introduction to vector
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C ALCU LEX Vtl General Statistical Program As advertised in April Your Computer.
The system can bo operated immediately without difficulty by anyone. They teach
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21 Headland Avenue, Seaford, Sussex

MACHINE

. ■ .keeps you in touch

Launched in July 1981, The War Machine was the first

magazine dedicated to computer gaming and has become

essential reading for those following developments.

Independent reviewers cover the latest computer-assisted

wargames and fantasy role-play ing/SF games. Leading software

authors describe the techniques they use to develop their

programs, and details are given for converting programs from

one brand of micro to another. Readers in eight countries share

details of the game-assistance programs they have written.

The emphasis is placed on games with lasting play-value. For

those who would like to write their own games software,

articles explain how general-purpose subroutines can be adapted

for different makes of computer. The magazine is now moving

into more sophisticated applications including the use of

Artificial Intelligence techniques to create a computerised game-

opponent, and computer- moderated multi-piayer games.

For a sample copy of The War Machine, send a cheque

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subscription is £13. Overseas subscriptions are handled by

airmail and a year's subscription is £20.

Emjay, 17 Langbank Avenue, Rise Park,
Nottingham NG5 5BU, England

38 YOUR COMPUTER, JUNE 1982

Ben Baruch leads you out of
some of the manual's dead-
ends and towards the centre of
the maze of mysterious BBC
functions.

You are trapped in a labyrinth called the
BBC Microcomputer. You have no previous
experience of this or any other labyrinth, and
so have only two possible means of escape: get
up and walk away — that sounds easy, but
most find it impossible in practice; alter-
natively you work out how to write programs
which look as good as Kingdom and Keyboard
— two of the best programs in the manual.

You begin perhaps to write programs with
pretty pictures in Mode 5, which seems —
according to the Guide — to be the only way to
obtain multicoloured graphics on the Model A.
Yet as soon as a program becomes interesting,
you run out of memory. You then may start to
find ways of compressing the program —
putting as many instructions as possible on
one line is a help — but that takes you little
further and, besides, now you cannot even
follow your own program. Kingdom is much
longer than anything you have written, so how
does that fit into the labyrinth?

Kingdom and Keyboard are written in
Mode 7, which gives you five times as much
memory to play with and Mode 7 has colours
and graphics and special effects. To obtain
colours type:

PRINT TAB(5,10)CHR$(&81) "This is red"

FILLING IN THE GAPS

Press return — and red it is* The instruction
PRINT CHR$(&8x)

will affect everything on that print line — x is
the logical colour. To set up a second colour
change in the line, use + . Thus

10 PRINT TAB(1,10}CHR${e8irThis © red"

+ CHR$(&83);
20 PRINT "and this is not"

will give you red and yellow in the same line.
Chr$(141) will give you half of a double-size
character. So

10 PRINT TAB(5J)CHR$(141);CHR$(&83»

"Hallo there"
20 PRINT TAB(5,2)CHR$<141);CHR$(&83)

"Hallo there"

will give you a cheery greeting when you Run.
Mode 7 graphics are produced by using
ChrS(&9x) instead of (&8x). Upper-cast
characters will be printed in colour, but in
place of lower-case characters, numbers and
other symbols — except " and @ and small
arrows — you will obtain block graphics in the
colour chosen. The letter space becomes a grid
of six cells, two wide and three high, and each
character fills in one or more of the cells.
Chr$(&FF) fills all six. Thus for example,

PRINT CHR$(&92)"5"
will print a rectangle one character high, half a
character wide and coloured green, which is
logical colour 2. A list of what each character
does is shown in figure 1.

Since provisional users arc left in silence by
the guide, try:

SOUND 1,-10,450,7
1 is the sound generator to be used; there are
four, numbered to 3: gives a kind of white
noise, the others give pure tones; -10 is the
volume which can be anything from to -15;
450 is the frequency; and 7 is the duration of
the note.

For a chord, each note must be preceded by
&a0, where a is the number of other notes in
the chord. For example,

SOUND &20V 10,300, 7

SOUND 8202,-10,320,7

SOUND &203,- 10,340,7
will give a three-note chord.

1

2

3

4

5

6

This is how a letter-space is treated by MODE 7 graphics

To till cells 6,1 6.2 6,2,1 6,3 6,3,1 6,3,2 6,3,2,1 6,4 6,4,1 6,4,2 6,4,2,1

Print

e

f

i

J

To fill cells 6,4,3 6,4,3,1 6,4,3,2 6,4,3,2,1 6,5 6,5,1 6,5,2 6,5,2,1 6,5,3 6,5,3,1

Print

I

m

n o p q r s t

To fill cells 6,5,3,2 6,5,3,2,1 6,5,4 6,5,4,1 6,5,4,2 6,5,4,2,1 6,5,4,3 6,5,4,3,1

Print v w x y z V* V*

To fill cells 6,5,4,3,2 5 5,1 5,2 5,2,1 5,3 5,3,1 5,3,2 5,3,2,1 5,4

Print + 6123456 7 8

5,4,1
9

Figure 1. The
full list to explain
the function of
each character
on the BBC
Micro.

To fill cells 5,4,2 5,4,2,1 5,4,3 5,4,3,1 5,4,3,2 5,4,3,2,1 4 4,1 4,2 4,2,1

Print :;< = >?()* +

To fill cells 4,3 4,3,1 4,3,2 4,3,2,1 3 3,1 3,2 3,2,1 2,1 1

Print ,-•/$%&'£!

YOUR COMPUTER. JUNE 1982 39

Wreak a terrible revenge on the
Martians who dared attack
Earth when you launch your
counter-attack with Paul
Edmond's Vic-20 space game
in Basic for the unexpanded
machine.

Mars IS AN arcade-type game for an unex-
panded Vic. Aliens, in the form of club signs,
build up from the bottom of the screen and by
moving your ship at the top of the screen and
firing, these aliens can be exterminated,
scoring two points each. Time and score arc
displayed at the bottom of the screen under the
baseline. Missiles arc occasionally launched by
the swarming aliens; these can be hit for a
bonus of fwe. However, you must dodge from
their path quickly — they are indestructible
and can steal 20 points from your score.

Owners of the 3K RAM expansion cartridge
will be able to unleash their artistic talents to
create their own graphics characters for the
aliens and missiles by using the high-resol-
ution graphics explained in the October issue
of Your Computer.

A handy Peek for the Vic is Peek(653). It can
be used to detect whether the shift,
Commodore, or control keys are being
depressed. For example,
10 8 - PEEM653)

SHIFT KEY; B = 1 COMMODORE KEY; B = 2
SHIFT + COMMODORE KEY ; B = 3
CONTROL KEY ; B = 4

Since this is independent of Peek(197) —
used for the rest of the keyboard — it enables
some keys to be used for left/right motion
through Peek(197) and the shift key for, say,
acceleration through Pcek(653) without the
two sets of controls interfering.

Try adding this to line 430, reduce the M
loop to 7 and fit in the Poke statement as
shown:
430 FOR M ■ 1 to 7: POKE 36865,

35+RND(1) # 6:NEXTMJ
36864 and 36865 control the X and Y positions
of the screen window. This addition to line
430 simply jiggles this window up and down.

*''**mm*ms***»;

• *s

jy

REfiDV.

1 TI*-"00000&" •P0KE3687S,15:PGKE36879,8

2 D I Mfl C 22 > : GOSUB890

3 21=7689+19*22

5 PRINT":!" = 2=7680 = PRIMT"tf?M««««M!l««:4 I I I I I I I I I I I I I I II I I I I J ■"

6 FOR I =1 T022 : flJC I>=1 ■ : P0KE76S8+22*22+ 1-1,121: NEXT I

7 PRINT"SW&ftttWHNG ON!"

8 FORV=0TO505 : POKE38400+V, 1NT<RND< 1 >*?>+l ■: NEXTV

9 P0KE36879,8:pRIHT ,, WWMW)fl

10 G=PEEK U 97 >:RT=0

11 IFRND<1X.3THEN19

12 D=INTCRND<1>*22; :RT=RT+1 :IFRT=4THEH19aFfiai)=0THEN12

13 FKD>=0--R=R+1 = IFR=15THENZl=Zl-22:F0RI-lT012:fKI>-l : NEXT I :R=0

14 PGKE21+B,83

19 IFTI*>"000130"THEN200

20 IFG=29THENX=X-1

21 P0KE36877..0

22 I FR/2= I NT < R/2 ) THENPOKE36377 , 220

23 IFO0THEN300

24 IFRNDa>>.9THEN300

30 IFG=37THENX=X+1

31 IFX<0THENX=O

32 IFX>21THENX=2i
40 P0KEZ+X1.32 X1=X
50 P0KE2+X,S1

59 IFG=32THEN80

60 PRINT^*M^!M«SI!!M«l'M«?I«!!I««BJ««!W .TSCORE"SC"TIME "RIGHT$<TIt J
4>

61 GOT01G

30 F0RI=1T019

31 P0KE36S76, 244-1*4

85 I FPEEK < Z+X+ 1 *22 > =88THENSC=SC+2

86 IFPEEK<Z+X+I*22>=65THENSC=SC+5 : P0KE36379, © = F0RP=1T080 : NEXTP • P0KE36879, 8
98 PGKEZ+X+I*22,93

100 I F I > 1 THENP0KEZ+X+ I #22-22 , 32

110 NEXT I : P0KE36876,

1 20 P0KE2+ 1 9#22+X , 32 : GOT060

200 POKE36877,0:FORR=1TO5:PRINT"^1«««« V0U 3C0RED"SC

218 FORU=1TO80:NEXTU

40 YOUR COMPUTER, JUNE 1982

220 PRINT\TiWMMM VOU SCORED M SG

230 F0RU=1T086 : HEXTU

246 NEXTR

250 PRIMTCHR$<142> :FORU=1TO100-NEXTU:POKE197,64-RUN

300 IFL=0THENQ=X

31 1 PGKE36875, 1 28+2*L

320 I FPEEK <Z+22#20-L#22+Q > =S1 THEN40Q

330 IFL>lTHENP0KEZ+22*23-L*22+Q, 32

340 P0KEZ+22* 1 9-L*22+Q .■ 65

350 I FL> 1STHEHL=0 : POKEZ+Q, 32 : P0KE36875, : GOTO30

355 POKE36875,0

356 L=L+4
360 GOTO30

400 POKEZ+Q, 42 ■ P0KE36877, 220 - PGKE36379, &

410 FQRT=15TG1STEP-1

420 PGKE3687S , T : PQKE36879, 8

430 FORM= 1 TO80 : HEXTM , T : PGKE36878 * 15 • P0KE36877 , •' SC=SC-20 : GOTO330

306 PRIHT"^W«««!ftM'!W«!iJ &WANT INSTRUCTIONS?!

310 GETA$ ■• IFA$=" "THEN810

820 IFA** ,, N ,, THENPRINTCHR*<142> =G0T03

825 PRINTCHR$<142>

330 IFA*<>Y ,, THEN810

331 P0KE36S79..S

835 PRINT'TEMRLIENS WHICH ATTACKED JSEARTH HAVE RETREATED 4HMM

i>M»iiiirro mars.

II

840 PRINT'^eWKW^WSMflT'OUR TASK IS TO KEEP THEM THERE UNTIL FURTHER HELP A

RRIVES. *'
350 PRINT"KS4ATCH OUT FOR THE JflDEVIOUS MISSILES'"

860 PR I NT "flWDP SHIT ANV KEVfi"

870 GETA$

871 IFA$0""THEN875

372 FD=Fn+FT- IFFD>9THENFT=-1

373 IFFIK1THENFT=1

874 POKE7680+5*22+FD-FT, 32 • PGKE7680+5*22+FD, 38 : GOT0870

875 PRINTCHR*<142>

830 PRINT H a»^C-MOVES VOU LEFTiM*«IM>-MOVES VOU RIGHTttiMiW'SPACE EAR -FIRE"
390 PRINT"SftWKWDM«W '••-IS VOUR SHIPWMttHELP ARRIVES IN 90«MI«!EECONDS"
900 PR I NT" ASMS SHIT ANV KEVS"

910 GETA$:IFA*=""THEN910
920 P0KE36879,8:G0T03

YOUR COMPUTER. JUNE 1982 41

iwmam

twmmm

IHH

IEJ

iwmm

1 I^HHB

a c omputrt **nion of the , ,
jiinvd bandit", with three reels. Nudge reel, and
Igi and GJmbV runctkxn. Incorporating
the VIC'f norroaJ graphic*, colour and sound,
it requires an evoanded VIC ( J/a

on the game ~BfttAK<
keyboard or a joystick controller

manoeuver the bat to try to break

ft w jf Require*

lick or keyboarv
• destroy incoming co r
protect your tuei dumps. Came ends when
mt hit or all tWt dumps destroyed. Uses det
paphscs. colour f sound. Hum in bask VIC only.

CARlCrroufcrie uMe, you can break the ban*

without risk of personal loss! Complete with IHt ol

oddi and allowed bets, you «re even £5,000 to

play wrtfv Came ends when you lose your shirt

Runs In any VIC. with colour and sound

5. HANGMA.

mooter at this version i
pen + pencil fame The VIC has a
vocabulary of 50 words, to which you can
Oestte or Replace your own words. Addict
colour * sound Runs in am

^-mJ

, TARKUS:

stretcher bearers to pkk up the wounded
and return them safefy to the red cross basr

you jh hH by an enemy mrs we. ho*

>ur>ded, on the Wd' O
addittfce, with defined graphics, colour 4 sound
Runs in bask VTC only.

NEW.

only ana do not represent

**£v

YtSS

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YC/6/82

42 YOUR COMPUTER, JUNE 1382

If you need to translate BBC
Basic into other Basics or are
just interested in the
development of computer
language Tony Edwards'
introduction to translation and
portability will be invaluable.
Although Basic dialects appear
so different that they might be
separate languages in their own
right they share many of the
same concepts.

The BBC COMPUTER* and hence its language,
has its origins in the Proton, the Acorn
machine which reached the prototype stage
but was never produced commercially. The
BBC Micro's language is> however, closer to
Microsoft Basic than is that of its ancestor the
Acorn Atom, and should cause little difficulty
in translation.

The commands, statements and functions
acceptable to the BBC interpreter are split into
two groups: the common-core and the exten-
sions. The idea is that the extensions should
not be used if a program is to be transportable:
the common core should be close to other
Basics and most interpreters should swallow it
without too much indigestion. On first sight,
however, the extensions seem alien to users of
other Basics and contain such additional state-
ments as Rcpcat-Until and Local.

The range of statements found in the
common-core subset of the language should
cause few problems in translation to other
Basics as they are all reasonably familiar.
There arc, however, some pitfalls. Not least
among them are variable names. BBC Basic
allows unlimited length of variable names and
all characters are significant. Thus the line
10 IF INCOME < INFLOW THEN GOTO 100

ELSE PRINT WARNINGS
may look acceptable, but if your Basic
evaluates only the first two letters of a variable
name you may be in trouble. Another problem
with variable names is that BBC Basic accepts
reserved words if they are lower case or
embedded in another variable name. Hence
the variable Poor may suit the BBC inter-
preter, but yours may not like it if Or is a
reserved word.

Punctuation can also cause trouble so you
should be on your guard. The well used and
almost universal question mark as an abbrev-
iation for Print does not appear in BBC Basic.
Instead ? 16000 returns the contents of address
16000 as would Peek(16000) and ?16000=10
puts 10 into address 16000 — that is, it serves
as a Poke 16000, 10. This should not surprise
Atom users, but those who use other machines
may be disconcerted. Also left over from Atom
Basic is n * ", but in BBC Basic it is no longer
a Rem, but a carriage return. Thus

PRINT"USE'YTHEV'NEXT" ' "LINE
returns:

USE THE NEXT
LINE
The remainder of the common-core should be
familiar to most Basic programmers and if
some of the functions it contains do not work
like those in your Basic, you should be able to
mimic them with little difficulty.

The statement ASC(AS) returns the ASCII

WE SPEAK
BBC BASIC

»*c computer

lllllMMI

o w

i& «•» a

character value of the first character of AS,
which should not surprise any one. If, how*
ever, AS is a null string, it returns the value -1
which may not be so obvious. Inkey/InkeyS
and Gct/Get$ are similar functions which read
the next character from the keyboard. With
the S, they expect a string — without it a
common variable. Most Basics do not have a
Get or Inkey but this can easily be mimicked
using VaL For example, in the place of

10N-GET
we would use

10 N$=INKEY$ : N = VAUN$)
Inkey is different from Get in that the former
waits a set time only for input — 10 ms for
each figure after the function. This, too> is
easily mimicked. The line

10N = INKEY(100)
can be translated as:

B$ = INKEY$
10 FOR I =0 to 1000
20 A$ = INKEY$
30 IF A$ = ""THEN50
40 A = VAL(A$):I = 1001
50 NEXT : IF A = THEN A= -1

This routine scans the keyboard for a fixed
period — you must adjust the length of the
loop to suit your processor — and returns the
value of any numerical key pressed in that
time. If no key is pressed, it returns the value
-1. The line may be necessary to alter the
buffer of keys pressed before the loop starts.

If you are trying to mimic InkeyS you will
not need the Val function in line 40 nor the If-
Then in line 50. There is a better way of doing
this with a Repeat-Until loop but more of that
later.

The BBC Basic's Restore statement is
standard, but an additional feature is the
facility to restore partly with Restore {line
number). This is not possible in most other
Basics and is a very useful facility. Unfor-
tunately it is difficult to imitate,

A direct answer is to adjust the Data pointer.
As a program is run the address of the next

Data line is held in protected RAM. The
Restore statement alters this so if you do not
have a partial Restore facility you must alter
this yourself with Poke statements. You
should first find from your instruction books
or other sources where this address is stored
and then Poke a suitable new value into it.

For instance, on the Genie or TRS-80 the
most significant byte is in memory address
16640 and the least significant one is in 16639.
Thus a partial restore statement on these
machines is

10 POKE16639,10 : POKE16640,200

To find out what values to Poke, Run your
program with

?PEEK(16639> : ?PEEK{16640)
in front of the Read statement which first
reads the line to which you wish to Restore.
This will then print out two values close to
those you need — close because any changes to
the program in lines with lower numbers than
the Data statements, including deleting the
temporary Peeks, will change the address of
the target Data line. You will have to change
the Poked values until the program runs as
you wish, remembering which address holds
the most significant byte.

This is the most elegant solution once it is
working. If, however, you think it too complex
you could start your program by Reading all
Data values into an array. Then call the
various values as the contents of array
elements as and when you need them, thus
avoiding Restore altogether. This method uses
a good deal of memory and causes the program
run to pause while the Data is placed in the
array.

There are a number of complex statements
in BBC Basic such as

FORN = 1 TO VAUA$)
or If-Then-Else which should be understand-
able even if your Basic does not have them.
You must split them into smaller steps for
your Basic. In the case of If-Then-Else you
{continued on next page)

YOUR COMPUTER, JUNE 1982 43

(continued from previous page)

will have to use a complex net of Gotos. As an

example, the line

10 IFA$ = 'YTHENENDELSEIFA$ = ''''THEN

A$ = "0" ELSEA$ = "X"
is probably comprehensible to you even if
your machine cannot understand it. Explain it
to your machine with the program:

10 IFA$*'Y I GOTO 100

20 IF A$ = "" GOTO 40

30 A$ = "X" GOTO 50

40 A$ - "0"

50 . ,..
100 END

BBC Basic includes user-defined functions
as part of the common-core. Those without
this facility will have to use subroutines
instead. To see how to do this consider the
following program in BBC Basic.

10 DEF FNSECANT«A,R) =
1/(COS(A + R*PI/2»

100 ANSWER = FN$ECANT{200,Z)
Line 10 defines a function called Secant which
returns the secant of the angle A plus R right
angles, and line 100 uses this function to
assign the result of this function to Answer
when the angle is 200 plus Z right angles.
Note the use of Pi as a dedicated constant
equal to n. This is simulated in other Basics
with:
10 B = 1/COSIA + R-3.14153/") : RETURN

100 A = 200: R-Z: GOSUB 10
110 ANSWER = B

In this program the subroutine in line 10 has,
fixed the variables A and R. Before the Gosub
the required values are assigned to these
variables for use in the subroutine. On return
from the subroutine, the result in variable B is
assigned to the required variable Answer.

The BBC Basic extensions have been added
to standard Basic in an attempt to improve it.
These extensions are extra facilities which
cannot be translated directly into other
dialects. However, if we understand what they
do, it is possible to simulate them in our own
dialect.

The Repeat-Until loop is probably the most
useful of these extensions. It allows a loop to
be repeated a number of times until some pre-
determined condition occurs which terminates
it. It is permissible to leave the loop with a
Goto and re-enter it later, and a single Repeat
can serve as multiple Untils.

When faced with such a function to translate
we must use some type of For-Next loop. This
is, however, full of dangers. Consider this sub*
program using Newton's Theorum of Succes-
sive Approximations to solve an algebraic
equation:
10 REPEAT

20 Y1 = A*X"P + B # X

30 X1 - X- <Y1-YMP*A # X"{p-1) 4- B

40 X3 = X : X - X1
50 UNTIL ABS (X-X3K0.001

This sub-program makes repeated estim-
ations of the root of the equation axP + bx = y
for given values of a,b,p,x and y. The root is
returned as X3.

When successive estimates differ by less
than 0.001, the program continues. Note that
BBC Basic uses A as the exponentation oper-
ator where you may use **,T> or [. When the
programmer writes this section of the program
he has no idea how many times the loop would
be implemented. This depends on the values
of the variables taken into the sub-program,
especially the accuracy of X the first approx-
imation of the root. We can assume that the
programmer has no control over the values of
these variables when the program i$ run. How
do we do this in a less sophisticated Basic? A
first effort would be:
10 FOR 1 = 1 TO 100
20 Y1 - A"XIP + B*X

30 X1 = X- |Y1-Y»/{P*A*X{(P-1> + B)

40 X3 = X : X = XI

50 IF ABS (X-X3K0.001 THEN 70

60 NEXT I

That looks relatively easy, but in line 50 the
program jumps out of a For-Next loop without

BBC Basic Equivatents

X = ASN(A) X = ATN(A/SQR(1-A # AH

X = ACS(A) X = ATN(SQR(1-A*A)/A)

X = DEG(A) X = A # 57.2958

X = RAD(A) X = A/57.2958

X = EXP(A) X = 2.71828 f A

Note that "f" means "to the power of"

Table t.

reaching the next. Will your Basic allow this?
If it does, how many times can you do it in one
Run? The problem is that the machine, not
having encountered a Next, thinks it is still
within the loop so at the next occurrence of
For it starts a new loop nested within the first
— the result is often disastrous.

A further programming error is in line 10,
Why put 100 as the upper limit of the loop?
Why not 1000 or 10? If you reach the upper
limit before ABS(XOC3>C0,00I, the program
leaves the loop with an inaccurate root in X3.
The answer is to use the biggest number
possible, but what is the largest limit your
Basic will accept, and what is the maximum
number of loops you will ever need?

Consider the program:
10 FOR i = TO STEP
20 Y1 - A*XIP + B*X

30 X1 = X- (Y1-Y)/(P*A*X«P-1) + B)

40 X3 - X : X = XI

50 I - NOT (ABS (X-X3K0.00U

60 NEXT

This works but is not clear just what it does.
This, in my view, spoils one of the best points
of Basic. Nevertheless, at times we must write
opaque programs when it is expedient.

When we work through this program to see
what it does, it becomes apparent that line 10
does very little. It assigns to the variable I,
incrementing it by each cycle of the loop
until it is less than 0. That seems like a dead
loop. Lines 20 to 40 are the sub-program as
before. In line 50, I is set to some non-zero
value if the escape criterion is reached, so line
60 will terminate the loop.

If the program will not run on your machine
some small adjustments will be necessary. If
line 50 is not acceptable to your compiler,
replace it with a more direct test;

50 IF ABS<X~X3K0.001 THEN I = -1

If your Basic does not leave the loop, test to

see if your compiler thinks is positive or
negative — mine thinks it is negative. So, with
a step of 0, it looks for a value less than the
limit to escape. You may have to assign a
positive number to I to escape.

If you use a ZX unit, the Repeat-Until loop
is easily simulated as follows:
10 (start of loop>
12
14
16

18 GOTO (Condition)- 10 + 10
On running, if the condition is false the jump
is to x 10 + 10 = 10. If the condition is
true, the jump is to 1 * 10 + 10 = 20.

You now not only have a translation for the
BBC Basic's Repeat-Until loop, but also an
efficient extra function to use in your own
programming. One word of warning: if the
escape criterion is not reached for some
reason, line 10 will loop forever. The Repeat-
Until loop also has this problem so unless you
are looking for a program with infinite
running time, I suggest it would be good
programming to add a loop counter which
aborts the loop with a suitable error message
after a reasonable time.

Armed with this new function you may like
to refer it back and find a better way to mimic
the Inkey function.

There are a number of useful trigono-
metrical functions in the extensions which are
not usually found in other Basics. They can be
mimicked directly using existing Basic
functions. Table 1 shows a selection of these,

A more exotic addition is the Defproc-
Endproc statement. The first statement will be
followed by a number of parameters in
brackets. You will have to assign a separate
subroutine to handle the operation of the
procedure and ensure that the variables used
in your subroutine are assigned the correct
values prior to the Gosub, Here the BBC
Basic code will help you as the variables to be
used in the procedure are those in brackets
after the Defproc statement.

A word of warning: BBC Basic allows the
local use of variables within procedures and
functions. Where you see the statement Local,
the variables that follow it will be treated as
different from earlier variables having the
same name. You should react to this by
placing a marker in front of the local variables
— that is, by calling the program variable XX
%XX. Alternatively, if you do not use double-
letter variables in your programming, double
the first letter when local values are used so
that the variable Time becomes TTtime. If
you do this remember your compiler may not
differentiate between TTime and TTop.

As a final warning this month I draw your
attention to the BBC Basic function Div. The
BBC computer has full floating-point arith-
metic, but it also supports this integer division
function. It is used regularly in programming,
especially in games. If your computer docs not
have floating-point arithmetic all is well as it
already believes that 5 ■=- 2 ■ 2. If, however,
you do have this facility, remember that 5Div2
docs not equal 2.5, so vou must substitute A =
B DIV C with A - INT(B/C) or A% - B/C if
you can use % as an integer marker.

Next month we shall look at graphics — the
major problem in the translation of programs
from one Basic to another.

44 YOUR COMPUTER, JUNE 1982

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YOUR COMPUTER, JUNE 1982 45

Do-it-your
Atom tool

David Berry shows how to
implement a toolkit of
mainframe utility routines
on an Atom,

Utilities are routines which operate on
programs, either to modify them or to assist in
their construction. The microcomputer
fraternity often refer to them as toolkits, and
the word "tool" is a very apt description. Like
all tools, a utility should be easy to use and
unobtrusive — a natural, unfussy, and above
all useful device, which can be picked up, used
and put aside again easily and quickly.

The utilities I shall describe all occupy little-
used areas of Atom RAM, they auto-run, and
return control after use to the base address of
the program being modified. Most make use
of sound output to indicate the stage of pro-
cessing the machine has reached, and employ
machine-code routines for maximum speed.

Programs are stored on the Atom in a very
simple text format. Each program line is
bounded by carriage returns which have the
ASCII code 13 or OD hcxademical. The Atom
always assumes that the first two memory
locations after a #0D contain the high and
low bytes of a program line number. The
whole program is always terminated with the
hexadecimal number FF, which appears in the
location immediately after the last # OD
carriage return.

Saving bytes

You may have realised by now that the first
byte of any given program must therefore be
# OD, and the last byte, at TOP-1, # FF. You
can check this, next time you switch your
machine on, by Pecking # 2900 and #2*901,
where you will find # OD and # FF
respectively. Now type a line number, try
000255, followed by a return, print &Top and
you will find that you have used only three
bytes — not the seven you may have expected.

This explains why you cannot used these
utilities on programs containing the line
number 255. The decimal 255 is FF in hexa-
decimal, and while the Atom is clever enough

not to be fooled at finding the program
terminator in a line-number position, the
memory-moving routines in these utilities are
not. So, if line 255 is present, the utility will
terminate prematurely. The same applies to
any line number which puts FF into the
second location after a # OD, i.e., the decimal
equivalents of # IFF, # 2FF, # 3FF, and so
on.

The machine-code routines for auto-running
and memory-moving usually sit directly on top
of the Basic text. This means that when you
copy the programs you must put spaces only
where I put them, and check that you obtain
the same value for Top as those quoted.

I made a major assumption when I started
writing Auto: that given a set of 26 labels, no-
one would ever use line numbers as targets in
Goto, Gosub and similar commands, and so
this program totally ignores them.

Every time the program is run it renumbers

Program description

Line 10: Initialise the program and input the
target program address.

Line 20: A points at memory locations
occupied by the target program. If
the second location contains the
program terminator, # FF, the
renumber routine is skipped.

Line 30: Subroutine b increases the line
number count by 10, Pokes the
new line number into its two
locations, prints it and moves
pointer A past it. Subroutine c
moves the pointer past the string
— program line — following the
line number. The sequence is
repeated until the program
terminator is found.

Program /. Auto,

-*>.«.- :-:• i-v

£nt*r ifrrdttTJ*
38D0G0S.b,G0S.c,U.^**FF

sexrHMU>;fi-a-2; 'a*«ff, "is«c,e.

39c*R+LENFt+i;R.

£nt*r txAo rurt roiJtllv* _

P«t2*CF C- Lltftf*23, STA1 8; STAG; LWW; STAS; JMPt C2F2,3

the program at which it is pointed. Secondly,
once renumbering is complete, or if the text
area is empty, it automatically generates line
numbers.

Auto is designed to live in the lower text
space between # 2800 and # 2900 - # 2900
is where Basic programs normally start.

Program 1 gives the Auto listing, the value
of Top you should strive for, and the *Save
addresses. Before you type in the program
remember to enter ? 18= * 28 first or you will
end up in the wrong RAM.

Address prompt

When you run the program it will prompt
for the most-significant byte of the address of
the first byte of the program to be renumbered
or entered. This will most often be # 29 — do
nor forget the # . To terminate the run enter a
return against the last line number generated.

The next two utilities need to be able to
move large amounts of memory quickly. By
that I mean that the contents of the memory
has to be moved from one location to another.
This is achieved by a machine-code routine
which, in its assembler source-code form, is
shown in program 5.

♦SAVE-ftUTO-aSvG

SO© 2SCF

Line 40: Start of generation of new line
numbers. The number is printed by
subroutine b as before, but now a
program line is input and stored.

Line 50: If the string is empty, move A back
two locations, Poke the program
terminator into that address, reset
the pointer in location 18 and
terminate.

Line 60: Continue the endless loop a.

46 YOUR COMPUTER, JUNE 1982

Memove itself is not a utility, but is simply a
means to an end and all it does is roughly the
equivalent of:

DO ?M = M?1; M = M + 1; U.?M=#FF
It just does it very, very quickly.

It is useful to enter Memove into the
graphics RAM starting at # 8200, where it is
clear of both the utilities and any test
programs you may later enter at # 2900. So,
type ?18-#82 and enter the program. For
this you can put spaces and lines anywhere
you like, with one exception: line 30 must not
be altered or added to.

For the adventurous

The more adventurous among you will have
tried using Auto to enter this program and,
even now, may be tearing out handfuls of hair.
In the interest of good will, to all readers:
enter:

!#8200=#FF0D
and try again.

Dele is short for "delete", which is exactly
what this routine does — it deletes blocks of
lines from the target program. It is also
intended to fit between # 2800 and # 2900, so
Poke #28 into location 18 before you start
typing. Enter the program exactly as it appears
in program 2 and check that your value for
Top is the same as the quoted one. Now enter
the auto-run routine as a direct command —
that is, with no line number. This assembles
the auto-run routine immediately on top of the
Basic text. Next, assuming Memove is still at
#8200, follow the sequence of commands
given which will change line 30 of Memove
causing it to be assembled into memory
starting at address # 28D8 — just above the
auto-run routine. *Save Dele using the
addresses given.

When you use Dele, you will be asked for
the most-significant byte of the target
program, and a start line number, SL=, and
end line number, EL = . Both start and end
lines are deleted together with all the lines
between them.

Squash is a compactor. It removes all the
spaces from the target program. Then, at the
user's option, removes all Rem statements
also. It is worth emphasising that it removes
all spaces. In some cases spaces are required
for the correct interpretation of Atom Basic
statements, and you should check chapter 10
of the manual if you find that your program
refuses to run properly after all the spaces
have been removed.

It is, however, clever in its handling of Rem
statements and can deal correctly with all
variations. Rems may be preceded by a line
number, label or semicolon. All of these
possibilities arc catered for.

Like Dele, Squash has to move large
amounts of memory to fill the gaps left by the

spaces and Rems it removes. To do this it uses
Memove and, since Squash and the machine-
code version of Memove add up to about
0.5K, it is too large for the usual RAM area
between # 2800 and # 2900. Since I rarely use
graphics mode 4, I decided that Squash could
best be entered from address # 9600 — that is
the top 0.5K of upper text space — and the
information given in program 3 is based on
that decision.

You can, of course, put it anywhere you like.
For example, you may be happier to use the
top 0.5K of lower text space. If so, replace

# 96 and # 97, wherever they appear in the
frame, with # 3A and # 3B respectively.

Follow the sequence in program 3 and you
will enter the program, assemble the auto-run
routine and, provided Memove is still at

# 8200 — if it is not, load it now- — assemble it
on top of the rest of the code. Do not forget
that your value of Top must equal the quoted
one or you will overwrite the end of the Basic
text.

When you run Squash it will prompt you for
the most-significant byte of the target program
start address. Then it will remove all the
spaces in that program and, if the shift key is
being held down when the bell rings, will
continue on to remove the Rems too.

Edit is unusual — it modifies itself as it is
running. It is a technique which will be useful
in a number of situations such as computed
Gotos using labels, or subroutine parameter
passing.

One of the useful things about interpreters is
that line number N + 1 is not read until line
number N is finished with. This allows line N
to modify line N+l, and this is the concept
used twice in Edit. In the first instance, line 40
changes the question marks in line 60 to
exclamation marks in order to speed up the
matching of long strings. Then, line 130
changes the From/To loop parameters in line
140.

Edit provides a facility for the global replace-
ment of strings. That is, it takes a string
entered from the keyboard and replaces every

identical string in the target program with a
second string entered at the same time. For
example: it can replace every Print with P.;
every In. with Input and so on.

You can also delete every occurrence of any
particular string simply by entering a null
replacement string — that is, just a return. But
be careful, you must make your search string
long enough to be specific to the string you
want replaced.

If you want to replace variable name E with
B and use as your search string only the letter
E, the program will replace every letter E in
the text. Next will become Nbxt, Let will
become Lbt, "Enter E" will change to "Bntbr
B", and so on.

Again this routine is too large to live at
# 2800 and it, too, was entered at # 9600, but
you can change this to suit yourself. The
whole process for entering and saving Edit is
shown in program 4.

Because Edit modifies itself by Poking
characters into its own program line, extra
care is necessary, when you enter the program,
to copy the listing exactly. Ever)' character and
space must be in the correct position or the
program may not run.

Speed comparison

When you run Edit you will be prompted
for the usual most-significant byte and for two
strings: SS= for the search string — the one to
be replaced; and SR= for its replacement.
This program docs not use a machine-code
routine for moving the memory contents and
is thus much slower than the last two utilities.
It may interest you to compare the speed of
removing spaces with Edit and Squash. By my
watch, Edit is no less than 40 times slower
than Squash.

To run any of the utilities, all you have to do
is mount the right tape and type

*RUN"name"

and the chosen routine will load and run auto*

matically. When it has finished control is

returned to the address given by

MSB * # 100

Program description

Line 10: Input most-significant byte, cal-
culate the first memory location of
the target program and input the
start and end line numbers.

Line 20; Find the start of a program line,
subroutine b sets Q equal to the
next line number which is then
checked against the start line
number S.

Line 30: Link to Memove until ?M becomes
equal to # D, use subroutine b to
find out whether the end line
number has been exceeded — if
not: repeat.

Line 40: Terminate the run.

Program 2, Dele.

NEW

Ent*r >*r w»* J*

10 IN. "ftSB-mM-rt^Mfclueej Jftl-I i IN. "SL-"S; IN. *El* - E

2CAD0 rwl+^U.^fD.GOS.bilFCKSiG.*

40 ?1$«N;E.

s©b0»m*»ioo*n?2;ft.

C**ch v*tu<r of Top equals #2€aflC
Enttr *uto-run rout in*
PM^3ftCX;L&^^»2e;S7Aie.STft ( ^■L&M^e;$Tft5;J^1PiCaF2;3

Cham* ?t#«»ovt' lift* 33 m& rvn.

MS»*S2
OLD

RON

S*v* f>ro3raft
*$AV£*BELE'2$0O 2*36 2SflC

Program 3. Squash.

Ready machine

Program description

?1S=#96

Line 10: input most-significant byte and

NEW

calculate the first memory location

of the target program. Subroutine
a jumps the pointer over text

Enter proar-am

enclosed In quotation marks and

10IH. l, MSB ,, M.;R=M;M=M*256.;DOGOS.a

line numbers, and searches for the

20IF?n=#20; ! #80=M; LI . #97Dy; M=M-1

program terminator.

30M=M+l;U.E;P.*7

(continued on next page)

(listing continued on next page)

YOUR COMPUTER, JUNE 1982 47

(continued from previous page)

Line 20:

Line 30:

Line 40:

Line 50:
Line 60:

Line 70:

Line 80:

Line 90:

Line 100:

Line 110:

Line 120:

Line 130:
Line 140:

If M points to a space, Hnk to
Memove to remove it.
Continue the Do loop until E is
true.

If the shift key is not pressed:
terminate.

Reset pointer M to start.
Stan of loop b, Gosub a then
check E to see whether the
program end has been reached.
If M is not pointing at a Rem state-
ment, increment it. The FF in the !
command masks out the character
following Rem.

If a Rem is found, run along it until
the statement terminator — either
; or # 0D - is found. S then con-
tains the number of characters in
the statement.

If this Rem starts with a line
number and ends with a # D,
adjust M and S so that the line
number is removed also.
If this REM starts with a ; and ends
with a # D, adjust M and S so that
; is removed.

If this Rem starts with a label and
ends with # D, M and S are
adjusted so that line number and
label are preserved.
In all other cases, increment S to
include the line terminator.
Remove all characters in this line
by linking to Memove.
Subroutine e.

(fisting continued from previous page)

4@IF?#E0@1=#FF;?13=R.:E.

50M=R*256

SubGOS.aJ IF E;?1S=R;E.

F0IF ! MQ#FF000008O#FF4D4552; M=M+1 ; G. b

S0S-0 i D0S=S+1 ; U. M?S=#3B0RM?S=#D

30 I FM?-3=#D I FM?S=#DM=M-3 ; S«S+3 ; G . c

i00IFM?-l=#3BIFN?3=#DM=M-l;S=S+l,G.c

110IFH?-i>#60IFri?-K#7BIFM?S=#D;G.c

126S=S+1

1 30cF. Q=IT0S; ! #80=M; LI . #97B8, N. ; G. b

140aE=8

150IF?M=#22; D0M=M+1 ; U. ?M=#22

160IF?M=#DM=M+3 .

170IFM?t=#FF E=1.;R-

180R.

Check value of Top equals #97B2

Enter auto-run routine

P=#97B2;CZ; LDflS#96; STfilS; STfiS; LDfl@8; 3TR5; JMP#C2F2.Q

Change "'MemoMe-' line 38 and run

?13=#82

OLD

38 P=97B0

RUN

Save Program

*SftVE"SQUflSH ,, 9600 9306 97B2

Program 4. Edit.

Program description

Line 10: Input and store the search and
replacement strings.

Line 20: Check that the strings do not over-
flow into the Basic work area.

Line 30: Input the most-significant byte and
calculate the first byte address of
the target program.

Line 40: Change the ? in line 60 to ! if the
search string is longer than three
characters.

machine

Line 50:

Start searching the target pro-
gram; jump over line numbers.
If the first, or first four, characters
of the search string match those
being examined, Gosub c; reset
the start of the search and replace-
ment strings on return from c.
Repeat until the program end is
reached, reset location 18.

Subroutine c:

Line 80: Return if there is a mismatch
between the search string character
and the one being examined.

Line 90: Move along one character; if this is

Line 60:

Line 70:

Ready

?18=#S<6

NEW

Enter program

10aP.$12;S=#21C;lN."*S- l< ;T=LENS;R=S+T+l;IN. -, *R=";P=LENR

2GHFR+P+1>#23F G.a

30IN. ,, msb ,, m;q=m;m=m*#i00

40J#9SB5=#3F3D533F; IFT>3; !#96B5=#213D5321

50M=M+l;DOM=M+l.; IF?M=#D M=M+3

68 1 F?S=?M BOS . c ; S=#2 1 C J R=S+T+ 1

70GOS. e; U. ?M=#FF; P. "END" ; ?18=Q; E.

80cIF?MO?S R.

90M=M+l;S=S+l.;IF?S<>#D G.c

100O=M; BGGG3. e; 0=0+1 ; U. ?G=#FF

110lJ=P-T;IFD=0G.d

120K=<<DS#+H :: >-#7f>/ , #80

130?#9782=#4E+K; ?#9787=#4E-K

140F.L=N TO N S.-KjH?L=?L;G0S.e;N.

150dM=M-T;IFF-0G.f

160Dd?M*?Rj M=M+i ; R=R+1 J U. ?R=#D

170*M=M-l;R.

1 80e?#B002=?#B002 : 4 ; R .

Check ualue of Top equals #97F1

Enter auto-run routine

P=#9?F1 ; i LDfl@#96; STR18; STft6; LBflSB; STfiSi JMP#C2F2;

Save proaram

*SRVE I, EDIT"9600 9800 97F1

not the end of the search string, go
back to line 80.

Line 100: Subroutine e generates a noise;
the rest of this line finds the pro*
gram-end location.

Line 110: Is the search string longer, as long,
or shorter than the replacement
string? D holds the difference in
lengths.

Line 120: If D is positive, K becomes +1;H
D is negative, K becomes 1 .

Line 130: Change line 140 to read O to M or
M to O depending on the value of
K.

Line 140: Move the memory contents for-
ward or backwards by D bytes to
eliminate or make room for the dif-
ference in string lengths.

Line 150: Move the memory pointer back-
wards to the start of the string. If
the replacement string is null, miss
the next line.

Line 160: Insert the replacement string into
memory.

Line 170: Go back one byte then return.

Program 5. Memove.

Read* (machine

?I8«#82

HEW

Enter jorosrau*

10 DIM LL2

20 FOR GN6 TO 1

38 P*iS>?D0

40C

50 LL8 LBY *SS;LDft *G,ST* #30; ItfV

6ft: LL1 LD*<#8e>,Y,BEY;STfl<f80>,V;STfl #3302

7& CHP d*FF,BE& LL2;INY;INY;BNE LLX

86 INC *ei;LItfU#80>,Y;DeC #8l;D£Y

98 5TFK#Se>,Y,INC #31 , INY; INY

100 JHP LL1

110-LL2 RTS

1203

130 NEXT

140 END

Save the j&ro*ra«

SAVE "nEKOVE" ■

48 YOUR COMPUTER, JUNE 1382

"Best explanation I've seen
. . . this is a must ' *

"Best independent software
package for the ZX81" *

MACHINE LANGUAGE MADE SIMPLE FOR YOUR SINCLAIR

Syntax # Magazine said: "it's the best explanation of Machine Language
for Machine Language beginners I've seer\ Its friendly style is painless
reading and simple analogies help make this language clear. TNs
introduction is a must."

Available as a quality paperback, 160 pages, £975 including post pack
and VAX

isofatzxsozxBiJ

UNDERSTANDING YOUR ZX81 ROM by Ian Logan

Dr. Ian Logan was the T981 winner of the Rosetta Stone Award* given

to the best independent product software package or application for the

Sinclair ZX80 or ZX8X for his perceptive insights into the way the ZX81 ROM

operates.

This book explains ZX80 Machine Language in terms of the ZX81 ROM,

giving numerous examples of routines from the ROM, and explains the

structure and organisation of the ROM, including routines from the ROM

you can use yourself.

A special section explains how to use machine code routines in your own

BASIC programs.

Available as a quality paperback, 164 pages, £9.75 including post pack

and VAX

>oa /'■

i £%

ZX81 ROM DISASSEMB1Y PARTS A & B

Dr. Logan is also the author of these two titles (see above) which are an

invaluable source of information for the serious ZX81 Machine Language

programmer

Part A lists all locations and subroutines in the ROM from OOOOH to OF64H

and covers all the operating functions of the ROM except the floating

point calculator.

Part B lists all locations from OF55H to 1DFFH and covers all the routines

involved in the 'evaluation of an expression' and a detailed explanation

of the floating point calculator'.

Part A 30 pages, £7.80 including post pack and VAT.
Part B, 84 pages, £8,80 including post, pack and VAT.

Other titles available;

Not only 30 programs for the Sinclair ZX81: IK

Not only over 30 programs, from arcade games to
the final challenging Draughts playing program,
which all fit into the unexpended IK Sinclair ZX81 but
also notes on how these programs were written and
special tips! Great value!
120 pages, £7.75

Complete Sinclair ZX81 Baste Course

The Complete Basic Course is a 240 page in-depth
comprehensive text for complete beginners and
experienced programmers. Over KX) programs and
examples illustrate the use and possibilities of the
Sinclair ZX81 This is on invaluable reference guide for
all ZX81 owners.
256 pages, £T8\30

Special Discount for ordering more than 1 title

If you order more than one title at a time, you get a discount of 80p per additional title:
If you order 2 books, deduct 80p from the total order 3 books and deduct £160; order 4 books and

deduct £2.401!

Orders to Metcourne House Publishers. 131 Trafalgar Rood. Greenwcn London S£K>
Correspondence to GteDe Cottoge. Station Road. Cneaangtoa Leighton
Buzzard. &=DS LU7 7NA

Nan 8

Address

Postcooe

The Complete S*rc*o* 2X81 BASfC Course
Basic Course Programs on Cossette
Mot Onry 30 Programs/Snciair 2X8V1K
Machine Language Programming Made Smpie
ZXQ1 ROM Disassembly Part A
ZX81 ROM Disassembly Part S
Understanang Your ZX$1 ROM

£lMO _

E3SO
£7.75 „
£07$ 1 |

£7.80

£830 □
19.75 G

Remittance enclosed £_.._ _. ,

Less Soeaal Quantity Discount £ „

MACHINE C

THE MISSING MONITOR

The ZX-81's monitor lacks the
facilities to after, search, set,
save and display memory and
copy the screen to printer
without clearing it. John
Sylvester's ZXMinbug, a
machine-code monitor,
remedies those shortcomings.

This PROGRAM provides the ZX-81 with a
machine-code monitor. It is 609 bytes long,
and resides in a Rem statement at the begin-
ning of the Basic program. ZXMinbug offers
the user what I consider to be the minimum
number of functions necessary in a monitor,
and is relatively simple to operate. The
method of entering the necessary code into the
Rem statement is left to you.

The first of the functions available is Alter
Memory. It means that the contents of any
RAM memory location can be inspected and
modified as required. The monitor runs in this
mode except when performing one of the
required functions*

Search Memory performs a search for two
specified bytes. If the search is successful, an

Table t

to 9 and A to F are used for data entry

Newfine is the field delimiter

H allows the user to set the parameters to

execute a subroutine
K allows the user to set the parameters to

initiate a search
L allows the user to set parameters to move

or set a block of memory
P allows the user to set parameters to do a

hex dump to screen
R resets the cursor to the start of the input

line
S saves the memory on cassette
Z gives a return to Basic

automatic dump is made to the screen, starting
at the location of the specified bytes.

A block of memory can be relocated any-
where in RAM with Move Memory, and Set
Memory enables you to set a block of RAM to
any value. The Save function ensures that data
in memory can be saved on cassette for future
loading.

Memory can be displayed on the screen in
hexadecimal code with Display Memory. The
display can be either static or dynamic. A
static display is not updated should any of the
locations dumped be changed. However, the
dynamic display shows all changes as they
occur,

The Copy function is really a return to
Basic, but on return the screen is not cleared
and so allows a copy of the screen to be output
to the printer. The user, by specifying the
start location, can execute a program and

return from the program to monitor is by
means of a Ret instruction. The keys used in
the monitor arc shown in table 1 .

When run either manually or automatically,
the display will clear and then present the
location 0000 and the contents of that location
on the first line. The cursor is shown as a
reverse character.

Pressing Newline will move the cursor to
the contents field. If you then press it again,
the memory location will be incremented by
one and the contents of the new location will
be shown; the cursor remains in the contents
field. If any changes are made to the contents,
the new value will be stored in the location
shown when Newline is pressed.

If R is pressed, the cursor is moved back to
the location field and a new location can be
typed. Note that all locations must be typed in
full - for example, for location 0120, 0120
must be typed and not 120.

Pressing Newline now will display the con-
tents of the selected location and the cursor
will be in the contents field ready to modify
the contents if required. When the R key is
pressed, if the cursor is in the location field,
any changes will be removed and the address
will be set to its original location where it
resided before any changes were made. If the
cursor is in the contents field, the cursor is
moved to the start of the location field and the
original value for the address shown will be
displayed — if, that is, any changes have been
made.

When entering an address or contents, the
cursor is moved to the start of that field when
the last character is typed. No changes are
made until Newline is pressed.

To operate the functions, press the required
key. Pressing Z will immediately return
control to Basic, Depending on how long you
press Z, an error code will be shown or Copy
will be displayed. The error code can be
ignored.

Pressing S will start to save data on the
cassette. If the Break key is pressed, the save
will be aborted and Basic will be entered. To
re-enter the monitor, just type Run and the
monitor will carry on as it was, except that the
location displayed on the input line will be set
to 0000. If a screen dump had been active this
will resume.

If you press H, which executes the program,
the location 40AC will be displayed and the
cursor will be in the contents field. Enter the
least-significant byte of the address of your
routine and press Newline; then enter the
most-significant byte of the address and press
Newline. The next location is the flag, so enter
01 and press Newline. The monitor has four
flags and constantly checks them, As soon as it
sees that the flag has been set, the routine will

be executed. The flag is automatically reset.

If K is pressed for a search, the address
409E is displayed. Set as shown in table 2.
The search will be carried out — it takes
between three and four seconds to search
65,535 bytes. If the search is successful, an
automatic dump is done regardless of whether
a dump is active or not. If a dump is in
progrcsss, the search dump will be dynamic. If
a dump had not been active, the dump will not
be dynamic. The flag is automatically reset
when the search is done. No indication is given
should the search fail.

P, which dumps memory to screen, will
display location 409B. Enter the following:
409B: (east-significant byte of the location at

which dump is to start
4Q9C: is the most-significant byte
409D: the flag, set to 01

The dump will take place. The flag in this
instance is not reset and so the dump always
remains active, not showing any change in
memory until the user resets the flag. Pressing
L, to move or set memory, displays location
40A5. Set as shown in table 3.

The L function can work in two ways: the
first is to move a block of memory, and the
second is to set a block of memory. In the first
case, it is essential that the address to which
data is to be moved does not fall inside the area
covered by the start address together with that
covered bv the block size.

Table 2.

409E: least-significant byte of the address

from which to start searching
409F: most-significant byte of address
40A0: least-significant byte of the amount to

search
40A1 : most-signrf rcant byte of the amount
40A2: enter the second byte to be searched

for
40A3: enter the first byte to be searched for
40A4: is the flag, set to 01

50 YOUR COMPUTER, JUNE 1982

Table 3.

40A5: least-significant byte of address from

which data is to be taken
40A6: most-significant byte
40A7: least-significant byte of address to

which data is to be stored
40A8: most-significant byte
40A9; least-significant byte of amount of

data to be moved
40AA: most-significant byte of the amount

of data to be moved
40AB: the flag, set to 01

In the second case, to set a block of memory,
enter into the first location of the block the
value to which the block is to be set. Enter the
parameters given, but in location 40A7/8 set
the address as that set in location 40A5/6,
incremented by one. That is the address of the
second location of the block. Set the amount to
the size of the block decremented by one. An
example is to clear — that is, to set to zero —
the block of memory between locations 4700
hexadecimal to 4800 hexadecimal.

Location Value

4700

00

first location block to
be set, is set to 00.

40A5

00 47

enter address of the
start of block.

40A7

01 47

enter address of the
second location of
the block.

40A9

FF00

enter the block size
minus 1 .

40AB

01

set flag.

The locations 4700 hexadecimal and 4800
hexadecimal will now be set to zero. The flag
is reset automatically.

Locations 4084 hexadecimal and 4091 hexa-
decimal in the main program contain the
addresses of the parameters for the various
functions: 4097 hexadecimal to 409A hexa-

decimal hold the variables used by the
monitor; 409B to 40AE are the parameters of
the various functions; 40AF to 40B6 contain
the table of control-key codes; 40B7 to 40C6
are the routine address tables and correspond
to the control-key table; 40C7 to 40EF contain
the routine to initialise the monitor. This sets
up the input- and display-area addresses,
displays the first location on screen and reads
the keyboard for future keyboard testing.

40F0 to 4122 holds the main routine. This
places a cursor on the screen then checks the
keyboard for an input. If a key has been
pressed, it then checks to see if the key is the
same as the previous key; if so, it ignores it. If
the key is different, the cursor is removed and
the character is found and then checked to see
if it is a data character or control character.

If the key is neither, it is ignored. If it is a
data character it is then displayed and the
cursor is placed in the next position. If it is a
control character, execution is started at
location 4141, and the address of the selected
function is calculated from the ATable and
KTable and control passed to that function,

4123 to 41 3F is the flag-check routine. This
is used when an invalid character is entered, if

The hexadecimal loader.

1 REH •* HEX UORbtft rOR ZXMIN
BUG

10 PRINT ,. "ENTER ERCH BYTE IN

HEX THEN Nyi_"

SO FOR X-16B14 TO 17123

SB FPST

30 SCROLL

49 LET XlsX-16394.

50 DIM Hl(4)

55 LET M$ tl> ■*'*"

60 FOR P*3 TO STEP -1

70 LET X2.INT (X1/(16«»PJ)

30 LET H$(4-P)nCH«$ (X2+26)

SD LET xi«xi- txa* ii&**P> >

100 NEXT P

105 SLOW

110 PRINT Ht,

ISO INPUT R*

130 LET H=(COOE R* C H -26) tf 16+ (C
ODE R* <2> -28)

14.0 POKE X^H

150 PRINT Af

160 NEXT X

Program 7,

1 REM MACHINE CODE IS HELD IN THIS
REM STATEMENT. THIS SHOULD BE
COMPOSED OF 609 CHARACTERS

2 RAND USR 16583

3 GOTO 2

4 SAVE "ZXMIN8UG"

5 GOTO 2

POKE 16510,0 (This gives the Rem line a line
number of zero, to prevent accidental
deletion).
RUN 4 (This saves the program and allows

automatic run on loading).
Notes: line 3 is needed to prevent a Save
function occurring when loading a program
saved by the save function in ZXMinbug. To
load a program saved by ZXMinbug enter
LOAD"".

no key is pressed or if the key pressed is the
same as that pressed previously. Each flag is
checked and if set the corresponding routine is
executed, if no flags are set, execution is
passed back to location 40F3.

4165 to 414B contain the routine to display
data on the screen; 417C to 4183 set or reset
the cursor; 4184 to 41 A3 are the hexadecimal
to display code conversion routine; 41A4 to
4 ICE is the display code to hexadecimal con-
version routine; and 41CF to 41F3 are the
initialisation routines for the flag-operated
functions.

The remaining locations are the actual
function routines. The keyboard is read auto-
matically by the ZX-81 during its display
routine and the monitor keeps checking
location 4025 to see if a key is pressed. If a key
is kept pressed, then the code remains in that
location. Therefore, to prevent the keyboard
repeating, a check is necessary to see if the
same character is present. If so, that character
is ignored until a different one is sensed or it is
set to FFFF, indicating that no key is pressed.

This means if the A key is pressed and kept
pressed, only one A is accepted, but as soon as
the key is released it will be sensed. This will
set 4025 to FFFF, so the same key can be
pressed again and it will register. If this was
not done, the character would be printed on
the screen so fast and so many times that it
would be impossible to set any data up.

Should you write a program in an address
greater than that specified in location 4014/5,
it will not be saved. I therefore recommend
that as usual, a Rem statement is created
holding enough characters for your program.
Having done this, run the monitor and search
for the Rem code and the code of the first
character used in the Rem statement.

It is advisable that the first two locations of
the Rem statement be filled with 76 (Newline)
to prevent a listing when back in the Basic
mode. The reason is that should the Rem state-
ment be listed, it may be bigger than the
screen and the ZX-81 will keep trying to fit it
on the screen. This results in the machine
hanging up.

The program can only operate on a ZX-81
equipped with a memory larger than 3.5K.
This is because it requires an expanded
display file.

If your ZX-81 has the new ROM, then the
addresses given in the listing as 40CA and
426D, contents CD 28 0E, should be amended
to CD 2B OF. Also address 4267, contents
CD 20 OF, should be changed to CD 23 OF.
(continued on page 53/

YOUR COMPUTER, JUNE 1982 51

ZX81 SOFTWARE FROM VIDEO SOFTWARE LTD IK & 16K

16K SOFTWARE price

£
VIDEO-SKETCH (ZX81 only). Move the cursor to
any part of the screen. Draw or rub-out as you
move it. Mix in text or graphics. Save picture in
memory. Save picture sequence on cassette. 7.95

VIDEO- PLAN (ZX81 only!. Performs the function

of an analysis book. Arithmetic functions include

addition, subtraction, multiplication. Printer

options. £7,95

VI DEO- AD. Rotating display of 16 pages of
advertising material. Set-up your own pages and
change them as and when required. £7.95

VIDEO-GRAPH. Planning and design aid. Create

pictures/charts/graphs and store within the

program. Save on cassette. Combine pictures like

an 'identikit'. £5.95

VI DEO- VIEW. Do it yourself teletext. Create

pages of data. Store them within the program.

Save on cassette. View on demand. £5.95

VIDEO- MAP (ZX81 only). Educational game

based on maps. Navigate your plane to its

destination. Bomb the target and return to base, £5.95

FORCE-FIELD (ZX81 only). Animated

bombardment game. You control the force-field

which protects your city against hostile UFOs. £3.95

SPACE- RACE (XZ81 only). Party game for eight
players. Rockets race to build stations in space.
Winners gradually take over losers until only one
winner remains. £3.95

TEST-MATCH, Realistic simulation of a test
match series. Dynamic scoreboard. Give each
player your own ratings for skill, technique, etc. £3,95

FOOTBALL- LEAGUE. Realistic simulation of an

entire season. Every match played and results

shown with progressive league table, You give

teams ratings for skill, effort, etc. £3.95

STOCK-MARKET (ZX81 only). An exciting game

of skill and judgement. Buy and sell stocks and

shares as prices change in response to world

events. £3.95

PACK 1 - VIDEO-PLAN + VIDEO-AD 17.95

PACK 2 - VIDEO-VIEW + VIDEO-GRAPH 13.95
GAMESET - VIDEO-MAP + 5 GAMES 19.95

1K PARTY TRICKS (ZX81 ONLY)

If you don't have a 16K RAM this set of programs
is for you. Ten separate programs — some
games, some more serious. All completely
original, all ten programs included in the price.

WHAT DO YOU RECEIVE

1 . Instruction manual.

2. Two copies of program on side A.

3. Audio commentary on side B. U6K only).

4. Built in demonstration. (16K only).

Cash with orders please.

Prices include VAT.

Mail order customers add £1.00 per order.

Allow 28 days for delivery.

4.95

NEW

VIDEO-INDEX

NEW

Q. How do you store 570OO characters in a 16K RAM.
A. Use VIDEO-INDEX.

Catalogue your cassettes, your record collection,
references to magazine articles. Amazingly versatile.
Capacity for 1000 individual references each of which can
generate 57 characters of text. Powerful search facilities
once the index has been created.

How is it done? The system cannot really fit 57000
characters in a 16K RAM. It gives the illusion of doing so by
eliminating duplicates. For instance in an index of articles in
computer magazines about the ZX81 certain words occur
time and again. VIDEO-INDEX detects these duplications
and thereby conserves space.

What do you get?

1 . A machine code master program which sits at the top of
RAM. This is initially loaded like a BASIC program.

2. A demonstration index containing 1000 references to
articles about the ZX81 in the popular magazines.

3. A detailed instruction manual.

You may then proceed to create your own catalogues and
indexes and save them on cassette.

This program is fast, efficient and ingenious and is by far
the best product we have introduced for the ZX81.

N.B. There isn't room for a commentary on this cassette

so you'll have to read the manual.
ZX81 orZXSO + 8K ROM.
ZX printer is useful but not essential. Price £9.95.

New Packaging.

We have discontinued our de-luxe boxed programs
except for PACK 1, PACK 2 and GAMESET. All
programs are now supplied in resealable "miniyrip"
plastic wallets.

SUPPORTED SOFTWARE

A new catalogue of software produced by named
authors is in course of preparation. Watch this space.

©

Stone Lane,

KlNVER,

Stourbridge,
West Midlands,
DY7 6EQ,

ENGLAND,

Td : Ksrai 24«2.

VIDEO

SOFTWARE LIMITED

Anmi P.S*cxIa.D t I**»jftr«»*W*e«M^

VXT |Uj.N* rtWMJ:

Persona/ callers welcome during office hours.
Send s.a.e. for further details.

52 YOUR COMPUTER, JUNE 1982

(continued from page 57)

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4124

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OK

A

CKECX PARITY

409>

00 00

jhfvt

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0000

CURSOR F01ITI0K

4127

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CALL

ro^ocxFx

IP rAKlTY 000 CAU ftOUTtXE TO DWF

4047

00 00

©LIKE

KCX

0000

START ADDRESS Or SCXCCM DUHF AREA

412A

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LO

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TEST SCAXC* OaC

4099

00 00

rjTATT

mx

0000

STAK? ADDRESS Of ISPVT TIILO

4120

17

OK

A

4091

00 00

©toe

mx

OOOO

FIRST AOOKCSS TO OUHF Off fCRCCK

4121

CA 17 42

CALL

ro.scAxc**

4090

00

DFLAC

mx

00

DCWF tlac

4HI

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LO

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4091

00 00

SAGO

xcx

oooo

start address or iLoac to search

41*4

17

OK

A

40a0

00 00

AMIS

MX

0000

LEKCTH «r BtOCX TO tXJAOl

41 n

u 45 a

CALL

FO,1tOVCS

40A2

00 00

WOK©

MX

oooo

DATA TO SCAJtat fOK

4m

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LO

A.fKL)

TEST EXEC FLAC

4044

00

sflac

mx

00

SeAKCR fLAC

4111

•7

OK

A

40AS

00 00

HAD©

XCX

0000

STAKT A00KCSS OF BLOCK TO HOVt DATA T*&X

4 I1C

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CALL

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40A7

00 00

0A00

wt

0000

STAXT AOOICSS OF itOCK TO MOTE OATA TO

4Mf

ll B2

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40*9

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AX7

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4141

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YOUR COMPUTER, JUNE 1382 53

(continued from previous page)

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54 YOUR COMPUTER, JUNE 1982

ZX81 or SPECTRUM

JOIN

ZX-GUARANTEED

(Club is devoted exclusively to the ZX81 . . . and Spectrum when available)

All games/progs are guaranteed error free. ZX-guaranteed is not just games, it is intended to be
educational to the user. Includes articles on BASIC, PEEK, POKE, MACHINE CODE, FLICKER
FREE PROGRAMMING, HINTS & TIPS, etc. etc.

Membership is April to April. If joining late, all current year's back issues sent. Membership £5 per
year. (Overseas £6.50. Outside Europe by air £11).

For sample back issue send £1 plus SAE

Send to: G.A. BOBKER, 29 CHADDERTON DRIVE, UNSWORTH, BURY, LANCS. BL9 8NL

Please enrol me as a member of ZX-GUARANTEED. I will complain like mad if errors found.

I enclose Cheque/P.O. /Sterling draft for

NAME

ADDRESS

r.

BARGAIN BYTES

FOR THE 16K ZX81

UNBEATABLE VALUE!

CASSETTE OF 8 PROGRAMS (50K+ )

One cassette of 8 programmes
50K Plus, all these for only £5

DEEP SEA ADVENTURE (14KJ. Discover the treasure chest before yoti
run out of gold or strength. Levels of play from "difficult" to "downright
impossible". Also has "Save Game" feature.

BANK ACCOUNT (13HKK Invaluable for controlling your finances.
Produces detailed statements and can also keep track of credit card
spending.

UNDERGROUND ADVENTURE 16%K), Battle against monsters and
obstacles underground. A very difficult and challenging task.
DEPTHCHARGE {2>6K). A skilful moving graphics game. Fire your
depthcharges to blow up enemy submarines before they destroy your
ship.

HANGMAN {11 fcK). The old family game based on a library of 500
words. Excellent graphics.

LOAN (27* K). Calculates repayments, time, sum borrowed or interest.
For Bank Loans or Mortgages.

C0DE8REAKER <2K). You have ten guesses at the four digit number
heid by the computer.

FOREIGN CURRENCY (3K). How many dollars is £110? How many
Francs is $38? See what your money will buy around the world!

ORDER NOW!

For convenience simply quote YC4 &r\<} your name and address on the reverse of your
cheque/postal order, and your software (on TDK cassette) will then be despatched.
first class post, complete with comprehensive instructions.

Send to:

Richard Shepherd, 22 Green Leys,
Maidenhead, Berkshire, SL6 7EZ.
l Telephone: (0628) 21107.

Trade Enquiries Welcome

INSTANT
INTERACTIVE
GRAPHICS
ON ZX81

LIGHT PEN SET pAQ Kfl

for the RD 8100 L ,_ Y»

(includes VAT & Pb?)
*DRAW complex graphics with ease on your

TV screen and avoid tedious line by line

programming.
* Revise your display and SAVE on cassette,

while your program runs.
•*Push pictures points and pixels with a poke

of the Pen and a program PEEK. Try our

VIDEO-TIDDLYWINKS!
*MENU SELECTION - without keyboard

entry.

The RD 8100 LIGHT PEN SET consists of the RD 8101 'MICRO-
MUM' MOTHERBOARD, the RD 8180 LIGHT PEN with
MODULE, and the RD 8100 SYSTEM MANUAL. Plug into your
ZX81 - and LOAD, from the FREE RD 8100 SOFTWARE
CASSETTE (IK and 16K), or write your own BASIC programs.
All orders are acknowledged, with a firm delivery date. Send
just €49.50 (VAT and postal charges are included) to:

R D Laboratories

5 Kennedy Road, Dane End, Ware, Herts.
SG12 0LU (0920 84380)

For details of the Full RD 8100 SYSTEM of ZX81 interfaces,
including Logic I/O, Analogue Input. Analogue Output.
8-Channel Analogue Multiplexer, Buffered Motherboard, send
us a stamp.

[>t>

YOUR COMPUTER, JUNE 1982 55

PROJECT

HAVE MICRO, WILL

John Dawson argues the case
for portability. He shows that
the idea of a micro in a
suitcase — or in this instance,
a camera case — need not be
the preserve of relatively costly
machines such as the Osborne,

Portability and communications are
becoming important trends in micro-*
computing. The Information Technology
revolution that is going on at the moment will
create a demand for information away from
orthodox outlets such as Telex machines,
VDUs attached to mainframe computers and
static microcomputers.

The Osborne 1 microcomputer exemplifies
one approach to portability — considerable
processing power with large-scale data storage
in a man-portable pack. In the early photo-
graphs advertising the Osborne 1 a compar-
ison was made between two men, one with an
ordinary briefcase containing sandwiches and
papers, and the second with the computer.
Leaving aside the advertising claims I was
always fascinated by the white knuckles of the
man carrying the computer — just how much
did it weigh?

The other approach is a genuinely portable
terminal with limited storage but with the
capability to access huge databases by way of
the public telephone network. The IXO tele-
computing system described in the April 1982
edition of Byte magazine is a fine example of
the shape of things to come.

Pocket terminal

The IXO terminal is about 6in. long by 4in.
or 5in. deep, is truly user- friendly, with excel-
lent ergonomic design, and has a single-line
liquid-crystal display with a QWERTY key-
board. There is a telephone Modem inside,
good security protection to make it difficult for
an unauthorised person to use your terminal,
or their own, to access one of your files on the
main computer, and the protocol you require
to access a database can be stored automatic-
ally in CMOS RAM.

EPSON is launching the HX-20 in the
States, a portable computer working on Nicad
batteries with a four-line liquid-crystal display
24 characters wide which will display upper-
and lower-case letters as well as the rest of the
ASCII set.

These new computers and devices are not
just marketing gimmicks. The ability to utilise
the power of a computer in several places has
already been shown to be very valuable. For
example, Government officials with terminals
coupled to a main computer by an acoustic

56 YOUR COMPUTER, JUNE T982

coupler have been helping farmers in the
U.S.A. for years.

doctors in this country have used portable
data capture units for analysing the electrical
activity of the heart for some time, and when
you couple a computer, rather than a dumb
terminal, to a central store of information, the
sky's the limit.

Having just finished writing Asimov, a
word-processing package for the Tangerine
Microtan, I wanted to be able to work on
papers and reports both at the office and at
home. I could have bought another Microtan
solely for the office and it would have been
fixed there with the same trailing wires; but at
the same time someone at work said that she
wanted a word processor for articles, press
releases and a book.

Below, the 5V PSU mounted Inside the camera
case. Right the micro that fits so neatly into the
case is mains-powered but could run for several
hours off a battery pack. Far right, the con-
nections to the word processor.

k

it %

TRAVEL?

processor unit and the several Tanex boards.

Furthermore, Microtanic Software which is
marketing Asimov, is also bringing out a high-
resolution board that will give a screen 64
characters wide by 25 lines and I wanted to
take account of that in the space left for future
expansion.

The case shown in the photographs has a
number of features that are particularly well
suited to this purpose. It is constructed out of
plywood with a thin aluminium veneer on the
outside and is quite rigid. Plugs and sockets
can be mounted directly on to the case and the
metal skin can be connected to the mains earth
without difficulty. The plywood is strong
enough to support a surplus mains power pack
for the computer. Indeed, fixing the power
pack in three places to two different panels
strengthens the case.

I stripped out the fancy foam padding and
ribbed side decoration and when I had Secured
the power-supply unit, I played with the
computer boards, the keyboard and the tape
recorder for some time.

Was there an advantage in having the boards
lying flat, and stacking one on top of another?
What effect would that design have on the
ventilation of the boards? Did the keyboard fit
over the tape recorder and, if so, was that an
efficient use of space, leaving room for the
connecting cables?

What about electrical safety? Could I bring
mains power round to the right-hand side of
the case, close to the signal wires, without
inducing mains noise and corruption on the
cassette and keyboard leads?

It seemed a good opportunity to share the
use of a portable word processor. The main
photograph on this page shows the result of a
weekend's work putting a new computer into a
portable case.

When I planned the project it seemed
reasonable to assume that a television would
be available wherever the machine would be
used. There is a TV in most homes, colleges,
conference centres and hotel rooms for some-
one who is travelling. Consequently, there is
no VDU built into the unit.

Railway work-station

If you want to use it on a train, you will need
a battery pack for the computer, like the
Osborne 1, and a battery-powered TV.
Printers are still expensive so I decided that it
would be an acceptable compromise to prepare
material on the portable work-station, store
the text on to tape and then print the text on
my own computer at home.

The text would be transported either as a
finished cassette tape or electronically along a
telephone line. This is essentially the same
method as a remote work-station in an office
preparing text and then printing the final
document on a central printer.

I like the Tangerine keyboard very much
and I wanted to incorporate it into the unit
without modification, m> the computer case
had to be wide enough to take the keyboard in

its steel plinth. After rummaging through
several luggage shops I found a version of the
case I finally bought but it seemed over-
expensive.

The same case is sold by Dixons camera
shops as the Chinon Cor niche, costing £29.95.
The Corniche is about 17in. wide inside and is
5.25in. deep, about 0.75in. taller than the
Microtan boards.

Asimov can *iiampulate about 7,500 words
when used with a fully-expanded Microtan —
or approximately 900 words with a full Tanex
board — and I wanted to leave room for a
Tan RAM card in addition to the central

I only constructed the computer after a good
deal of thought. Destroying the guarantee on
£30's worth of case by drilling holes in it is
always rather an anxious business, but it
turned out well.

The keyboard resrs on two side steps when
it is in the case and the steps are deep enough
to support the keyboard sufficiently clear of
the National Panasonic Slimline tape recorder
to store some cassette tapes between the two.

The mains input is on the left-hand side of
the case and a lead is taken underneath the left-
hand step to a neon light on the front surface.
(continued on next page)

YOUR COMPUTER, JUNE T982 57

(continued from previous page)

There is no on/off switch; when you plug the

computer in, it is on.

I completed the mains wiring before doing
anything else, bringing a lead out to the right
side for the tape-recorder power. The next
step was to fit the keyboard and measure the
space remaining for the computer boards. I
used a spare mini-motherboard and mounted
the CPU and Tanex cards upright and as close
to the partition between the keyboard and the
rest of the case as possible.

Screen expansion

By hand-wiring a bus to two or more Euro-
card sockets, I expect to be able to fit the
Tan RAM and big screen boards in the space
at the back of the case. The aluminium panel
separating the power-supply unit from the
computer is bolted to the back of the case and
to the unit*

It is carefully earthed both to act as a
Faraday screen and to protect the computer
should a mains lead come astray from the
input to the power-supply unit.

The 16-pin dual-in-line plugs and sockets
were never designed for frequent connection
and disconnection; if you do not believe me
look at the amount of metal in the Military
Specification socket shown in photograph 9
and remember that it was designed to cope
with salt water, mud, vibration and parachute
drops.

Accordingly, I cut the keyboard cable on the
Microtan and used a 25-way D plug and

socket to connect the keyboard to the
computer. Radio Shack has plastic D plugs
and sockets with fittings to couple directly to
ribbon cable.

The clamp on the back of the plug is
comparatively fragile and it is easy to break the
side arms that hold the back in place. The
chrome bar on the right-hand side of the case
is intended to protect the sockets from damage
when the computer is moved.

Before doing anything with the computer I
switched on the power-supply unit and
checked the mains volts and the output volts.
Remember to switch off before going any-
where near mains voltages — at 230V AC, the
mains can kill you.

If you want to check mains voltages connect
the multimeter and then switch on to obtain
your reading. If it is impossible to do that then
at least keep one hand in your pocket which
will substantially reduce the chance of your
receiving a shock through both hands across
your heart.

The output socket from the modulator on
the Microtan protruded too far and I removed
the socket, soldering a coaxial lead directly to
the unit. When I plugged the central-processor
unit board into the motherboard and switched
on, it worked. When I plugged the Tanex
board in beside the CPU card and switched on
it functioned until I added a full set of RAM
chips.

Then it worked for just half a second before
failing completely. There was no time to see
an organised pattern on the VDU and then the

screen went blank. I checked the Tanex board,
which I had made from a kit, and resoldered
many of the joints, looking always for thin
whiskers of solder that might short out the
power supply. Nothing obvious, even under a
magnifying glass.

Eventually I connected a low resistance
across the power-supply unit with a multi-
meter in scries to measure the current the unit
would put out before it shut down. After
adjusting the current limiting variable resist-
ance to allow the supply to give at least 1.5 A, I
reconnected the computer and the Tanex
boards. This time it worked; it was just coinci-
dence that the difference in current drawn by
the Tanex board with the full complement of
RAM was sufficient to shut dow r n the power-
supply unit.

CONCLUSIONS

■The whole case weighs about 10 kgm.
when it is packed.

■ Asimov is easy to use, and the VDU sits
comfortably on top of the computer case
— the facility to do work on a word pro-
cessor and to take the machine with you at
night or at the weekends is splendid.

■ If flat screens are developed to the stage
where they are cheap and reliable in the
near future I shall be tempted to mount one
in the lid of the computer case so that I can
write on the commuter train.

■ The final touch would be an acoustic
coupler to transmit and receive text down a
telephone line.

58 YOUR COMPUTER, JUNE 1982

NEW PROGRAMS FOR
THE UNEXPAIMDED VIC 20

PRC2 FLYSNATCHER

Superb colour and sounds as the weasel, who has an unfair
advantage, chases you. Your only escape is to eat the flies and
dive into a bush!

PRC3 ANT RAIDERS

The ants very gracefully shuffle around the screen while you
try to shoot them. Easy? Just try it!

PRC 4 SUB ATTACK/MISSILE COMMAND

Two great, noisy, colourful games. Sub Attack — a big fun
torpedo firing range! Missile Command — fire to destroy the
mutants while dodging their deadly touch!

PRC1

WAR, SMASHOUT, BLACKJACK, LOGIC, PICK-UP GAME,
ALARM CLOCK. Our six program best selling introductory
cassette.

EACH CASSETTE IS ONLY £7.50 INCLUSIVE

Please send □ PRC 1 □ PRC 2

I enclose cheque/PO for £

NAME

JPRC3 UPRC4

ADDRESS

PR SOFTWARE

28 THE FAIRWAY, SOUTH RUISLIP,
MIDDLESEX HA4 ORY

COLOUR
ATOMS

Colour Atom (ATM3)

£197.80

Acorn Atom ass. 5Kram 8Krom + new PAL Colour
Encoder, 1.8A power supply and 4 free Acornsoft
cassettes

New Colour Enncoder (ATM25) £43.70

ATM10 Atom Kit 2Kram8Krom ...£132.25

ATM11 Atom Kit 12Kram8Krom .,...£155.25

Acornsoft cassettes ;... £10.81

BBC21 Upgrade Model A to B £115.00

Prices inc. of VAT and Postage

All items in stock — quick delivery

o

Electronequip

128 WEST STREET, PORTCHESTER

HANTS P016 9XE

TEL: 0705-325354

&80

hi*

AN

« tamtam t»»r»»m

ACCESS THE OUTSIDE WORLD!
EXPAND & IMPROVE YOUR ZX PIECE BY
PIECE WITH OUR SPECIALISED PRODUCTS

TE10 INPUT/OUTPUT PORT - Easy to use. Fits
betwen ZX & RAM PACK/PRINTER (if required). No
skill required to connect. Can be used for such things
as:— motor control; sound/music generators, con-
nection to printers/floppy discs/light pens/other
computers, temperature monitoring, square wave
generating, control of rotating aerials, even train sets
etc. Port has 16 programmable 1/0 lines and may be
used without any electroncis knowledge to connect
other add-ons. Motherboard required ONLY when
two or more add-ons are used at any one time.
FULLY ASSEMBLED £17.95p.
KIT (WITHOUT CASE) £14.95p.

TE12 4 CHANNEL RELAY BOX - TO SUIT
PORT. Contact rating:- 240v AC/1.5A - 24V DC
or 110V AC/3A. Up to 4 units i.e. 16 relays can be
operated. £14.95p.

TE15 8 WAY TRANSISTOR DRIVER - £9.95.

TE17 8 WAY SWITCH UNIT (EDUCATIONAL) -
£12.95p.

TE18 8 WAY INDICATOIR UNIT ( " I - £12.95p.

TE 20 JOYSTICK & FREE GAME - (2 Joysticks
may be connected via Motherboard.) £12.95p.

TE30 MOTHERBOARD - Allows multiples/com-
binations of add-ons — up to 16 1/0 lines may be
used - £15.95p.

TE126 POWER SUPPLY - 6/7.5/9V DC at 300 mA
— Required for use with add-ons TE12/15 &• 18.
£4.95p.

23 + 23 WAY ZX Edge Con £2.85p. Contact cleaner
£2.30p.

16 WAY SINGLE SIDED EDGE CON £1.95p.
EXTENDED PIO NOTES £1.

PRICES INCLUDE VAT

Receipts always provided — Delivery normally ex-
stock. ADD 50p towarsds p&p on all orders under
£20.00p, with the exception of accessories, e.g.
Edge con. Full instructions and examples with all
products.

SEND S.A.E. FOR CATALOGUE.
POSTAL OR TELEPHONE ORDERS ACCEPTED.

_, THURNAU (ELECTRONICS) EHG
DEPT Y, 95 LIVERPOOL ROAD,
CA0ISHEAD, MANCHESTER M30 5BG
TEL: 061-775 4461 (24 hour)

YOUR COMPUTER, JUNE 1382 59

YOUR COMPUTER

is your magazine — every issue is
full of articles specially written for
the home computer enthusiast.

Reviews of personal computers;
Programs; Surveys of software available
on the market; New application ideas for
your computer; Computer Club — news
from your clubs, Calculator page; Letters;
Answers to your problems and pages and
pages of computer games
and program listings

All for only 60p

Ensure your copy

each month, take
out a subscription

NOW!

moving ahead

with

ZX software

ZX CHESS & ADVENTURES

PROGRAMS FOR THE ZX81/80 INCLUDING -

Very popular machine code program, with six
levels of play and an analysis option. Unbeaten
except by:

A new improved version, wrih a faster
response time, seven levels of play, and in
addition a recommended move option.

Exciting machine code games with instant
response, choose from the range below. You
find yourself stranded on an alien planet.

Can you reach your ship and escape?

In a jungle clearing you come across an inca
temple. You must break in, collect treasure and
escape alive. Bewaie. Includes a cassette save
routine.

You are unfortunate enough to be drawn to
an alien cruiser. Can you reach the control room
and tree yourself or will they get you first?

Includes a cassette save routine.

GALAXY WARRIOR £3.00

Fast and exciting interactive animated graphics game.
Hunt cttngons and go through black holes . .

1K GAMES PACK £6.00

and many more. For a catalogue givin^ full details, please send a S.A.b to:

GALAXIANS £6.50

AH the features of the arcade yame in a fast machine code program.

Swooping attacks, explosions and personalised scoring.

ZXBUG £7.00

A 30 in 1 machine code tool and disassembler, allows access to registers

and search through and modify memory; with cassene routines,

Artie Computing,

396 James Reckitt Avenue Hull, HU8 0JA

ZX CHESS I
reduced to £6.50

ZX CHESS II
now only: £12.99

ADVENTURES

ADVENTURE 'A'

£6.00

ADVENTURE B'
£7.00

ADVENTURE C
£8.00

TWO GREAT ZX81
16K CHESS GAMES

ZXCHESS (ENHANCED)

•Written totally in machine code.

• Ful! graphic display of Chess board,

• Six levels of play: Two play within competition time limits.

• Option to play Black or White.

• Plays alt legal moves including castling and en-passant.

• Cassette routines for saving unfinished game and returning to
later.

• Displays moves of game on screen or printer for analysis.

• Print a copy of the Chess board onto the printer.

• Board can be set up in any position, you can even swap sides
midgame.

• Clear whole board with one command: for end game analysis.

£6.50

ZKCHESS ii We believe the strongest 2X81 Chess game as

no other has beaten itH
•All the features of 2XCHESS plus:

• Book of 32 opening moves.

• Seven levels of difficulty: FOUR play within competition time
limits.

•A move is suggested by the ZX81 if wanted.

•Optional Full Graphic version using the QS CHRS Board.

£12.99

2 copies supplied on cassette with full instructions.
Cheques and postal orders payable to:

COMPUTING

ARTIC COMPUTING

396 JAMES RECKITT AVENUE,

HULLHU8 0JA

vha

60 YOUR COMPUTER. JUNE 1982

RESPONSE FRAME

Do you have a problem? Your manual is
incomprehensible or you just cannot get the
hang of that programming trick you tried —
whatever it is, Tim Hartneil will do his best to
answer your queries. Please include only one
question per letter and mark them "Response
Frame".

IS IT WORTH IT?

■ 1 own a IK ZX-81 and want
more memory. Is a Vic-20, BBC
Micro or Acorn Atom worth the
extra money when compared
with expanding the ZX-81? If so,
do they run on Pet, or similar,
Basic?

Edward Hogarth,
Preesall, Blackpool.

The real answer must begin "it all
depends". It all depends on what
you want to do with your micro-
computer. Certainly, if you want
music, colour, reliable Load/Save
and Pet Basic, the Vic-20 is worth
the money. If you want a computer
with high-resolution graphics that
you are unlikely to outgrow for
years, the BBC Microcomputer is
worth the money. Certainly if you
do not mind working in what Clive
Sinclair once called an "arcane"
version of Basic, and you want a
good reliable machine, which
positively begs you to experiment
with assembler, the Acorn Atom is
worth the extra money. Sinclair's
new Spectrum, reviewed on page 20,
may also be worth considering. First,
determine exactly what you need to
make the most of your micro-
computer, then examine the com-
puters you can afford.

WHAT PRICE FAME?

■ 1 write Basic programs, and I
imagine — like the majority of
others — partly for their applic-
ations, but mostly for the fun of
it. However, there are occasions
when, having spent many even-
ings writing, testing, and de-
bugging a program, one thinks
that it would be good to earn a
little cash for one's labours —
perhaps to buy a printer. Do you
think it would be possible for
Your Computer to provide some
information on the possibilities
which arc available, assuming
that one does not want to get
involved in setting up one's own
business? For example, can one
sell programs to the many small
software firms which advertise
monthly in Your Computer, and
what is the situation regarding
copyright?

Terry Peppard,
Redhill, Surrey.
The easiest thing to do is to give
software companies the right to dup-
licate and distribute the programs on
your behalf. We would suggest you
approach the bigger companies first
— such as Bug-Byte, Artie or
Premier Publications — as they are
most likely to have a well-structured
arrangement in existence to cater for
such situations. You automatically

have the copyright for any original
work — be it a musical composition,
a book, a computer program, or
whatever — but you cannot expect to
have the rights to some program you
have merely adapted from a
published listing. It is best, in terms
of financial return, to sign a rights
deal only, rather than sell a program
outright. Your Computer also pays
£6 for every Software File contri-
bution published and £35 a page for
articles in the main section of the
magazine.

THINK OF A WORD

■ I have had a Vic-20 for some
weeks now and am pleased to see
that Your Computer is devoting
more and more space to the Vic.
I wish to write a program in
which the Vic thinks of a word,
rather than a number, but I
cannot work out a way to make
the Vic think of a different word,
short of having all the words in
one string, and having the com-
puter select a part of the string. I
would be very grateful if you
could suggest a way for me to do
this.

S Harmwody
Irvinty Scotland.

If you hold the words in Data state-
ments, vou just need to have:

FOR J = T TO INT(RND(1)*X)
where X is the number of words in
the list

READ A$, NEXT J
This will move through the list a
random distance, ending with one
word equal to AS, Of course, if you
decide to find another word at
random during the same game, you
will need to add a Restore statement
before the opening of the J loop.

IT WAS THIS BIG

■ I own a 16K Sinclair ZX-81,
and wonder if you could suggest
a short program telling me how
much free memory I have left in
my machine while I am entering
a program.

J Taylor,
Askam-in-Furness, Cumbria.

A one-line program which will help

you assess free memory is

9999 PRINT PEEK 16396 + 256* PEEK

16397 - 16609
Just enter Goto 9999 when you want
to find out how much memory your
current program has used.

EASY AS ABC

■ Having just acquired a ZX-81,
I looked through numerous com-
puter magazines and found you
are the most interesting and

helpful, and I have ordered a
copy every month. I have been
looking for a program which I
can use which would take a
random list of items and put
them in alphabetical order. So
far I have had no success, and I
wondered if you could help me
with such a program. I am build-
ing a library of records, and am
now using my ZX-81 to list them,
but it would be of great help if
the list appeared in order.

C A 7 McPhersott)
Harrow.

The following program should
suit your needs. It will run in one
IK, although you will only sort a
limited number of items with that
small memory. If you would like it to
list items in the opposite order to the
one it now uses, change line 175 to

FOR T = Q/G TO Q
Thank you very much for the com-
ments on Your Computer.

1 REMALPHASORT

2 PRINT "NO. TO BE SORTED?"

3 INPUT Q

4 CLS

40 DIM A${Q+ 1,10)

50 FOR T-Q/QTOQ

60 INPUT A$(T)

70 NEXTT

80 FOR Z = 0/0 TOG

90 FOR T = Q/Q TOO
100 LETB$ = A$(T)
110 IF A${T + T/T)>«A$(T)

THEN GOTO 130
120 GOTO 150
130 LET A$(T)-A$(T + 1>
140 LET A$(T + 1) = B$
150 NEXT T
160 NEXT 2
175 FOR T = Q TO Q/Q STEP

-Q/Q
180 SCROLL
190 PRINT A$(TI
200 NEXTT

IK ADVENTURE

■ I am 12 years old and have
recently bought a Sinclair
ZX-81. In countless magazines I
have seen adventure games for
higher-memory computers. As
you know, this standard
machine only has a IK RAM,
and I have never seen an
adventure game fox a IK ZX-81.
My money resources will prob-
ably never expand to buying a
Sinclair 16K RAM. Could you
possibly tell me where I can find
a program of adventure for a IK
computer?

Lee Jolly,
Preston, Lancashire.

The short answer is no. There is
no way you can fit an adventure into
IK. The longer answer is made up of
three possibilities:
■You buy cheaper expansion

memory. 3K packs aic available

for around £15.
■Alastair Gourlay's book 34

Amazing Games for the ZX-81 has

a IK Wumpus game in it which,

although necessarily limited, is

possibly of interest.
■You take advantage of the fact that

[he ZX-81 can stoic variables such

as

LET A$ = "A BIG BAD BOOGY"
when entered directly, and these can
be used in a game if you use Goto 1,
rather than Run.

BBC GAMES

■l have written a board game
for my BBC Microcomputer,
and although the display —
using full stops, the letter H for
the human piece and C for the
computer piece — is satisfactory ,
1 would like it to place each piece
in a particular colour. How can I
do this?

John Q'Rorke,
West Ruislip.

If you USE the Une:

F - - 130*{M-67) 133*(M-72)

134*<M^46>
and you are working in Mode 7, you
can follow it, if M is the code of the
piece 3 with the line

PRINT CHR$(F);CHR$<M);
to obtain purple Hs» green Cs and
light-blue full stops, Change the
numbers before the brackets in the
first line given to produce different
colours for the pieces.

IS VIC THERE?

■ I read about the Super Vic in
Your Computer. I was about to
buy a Vic-20, but now I am
worried that die Super Vic will
replace the Vic-20 in the same
way as the ZX-81 did the ZX-80.
Could you tell me more about
the Super Vic and if the Vic-20 is
expandable for a similar price?
M P Eaglen,
Wroxell, Isle of Wight.

The super vrc provides 40
characters per line, and more on-
board memory than the Vic-20.
Although this is much better than
the Vic-20, the standard Vic is avail-
able now, and it is possible to obtain
high-resolution graphics through a
software routine. You may be wail-
ing a long time for the Super Vic to
be available in the U.K. Therefore,
there seems little point in delaying
your purchase. More information
about the whole Commodore com-
puter range, including the new
U hi max, can be obtained at the
Commodore show in June.

HEAVY KEYBOARDS

■I am looking for a heavy* duty
keyboard that will house my
ZX-81. The two that have
attracted my attention are the
Fuller FD system and the Protos
keyboard, both recently advert-
ised in Your Computer. I was
wondering which one of these is
the better, or if there is a better
one on the market. My price
range is £70.

Simon Tylei,
Warrington, Cheshire.

You have not specified what you
mean by heavy-duty so it would be
difficult to recommend a particular
keyboard. For a detailed account of
ZX-81 keyboards read Stephen
Adams* article in thi* issue.

YOUR COMPUTER. JUNE 1982 61

ZX81

users

I need more memory!

please rush me within

10 days, the fully assembled,

tested and guaranteed

'BYG BYTE*

16KRAM

Name

Address

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with tddtmn
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4118 200ns 3.38

2716 350ns (+5v) 3.59

4164 200ns 4.65

2716 (3 rail) 450ns 5.95

4516/4816 100ns 3.25

2732 450ns 3.90

5516 200ns 9.38

2732 350ns 4.40

6116 200ns 5.10

2532 450ns 3.90

61 16LP 200/1 50ns 7.61

BBC MICROCOMPUTER UPGRADE KITS

BBC 1 RAM Upgrade Kit

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BBC 2 Printer User I/O Kit

9.50

BBC 4 Analogue l/P Kit

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225

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WELCOMC CREDI. LmRO USERS F^\ ^ AVAILABLE

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Programming the

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1 7 chapters, appendices, ana index,
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62 YOUR COMPUTER, JUNE 1982

FINGERTIPS

Fingertips is our regular calculator column
covering calculator news, programming hints
and examples of unusual applications. The
column is written and compiled by calculator
enthusiast David Pringle who is glad to hear of
any of your ideas. Your Computer pays £6 for
each of your contributions published.

With ax enhanced 12K ROM
Basic, six new programmable
function keys and an advanced four-
colour graphic printer the Sharp
PC- 1500 is a new, super-improved
version of the PC-12I 1. This newly-
released machine, which wc hope to
review fully next month, set me
thinking about what we really
wanted from the next generation of
pocket calculators. Is it really to be a
quest for a mini-microcomputer, or
will improved Basic with better
array and string handling suffice?
Indeed, do we want Basic at all?
What about memory capacity, peri-
pherals and keyboard layout? If you
have any opinions on these matters
write in to Your Computer, Finger-
tips.

Dale Cass of Stafford has an inter-
esting program for writing banner
messages with the Casio FP-10
printer. To operate, the user simply
enters the codes of the letters of the
heading into memories MOO to MO 3,
Five letters may be stored in each
memory, and each is represented by
a two-digit number corresponding to
its position in the alphabet. For
example, the message Your Computer
would be entered as
25.15211827 in MOO
3.15131621 in M01
2 0.0518 in M02

Note the decimal point after the first
two-digit code.

This is the only method for enter*
mg letters as the calculator has no
string-handling facilities. When the
numbers have been entered — and
terminated by a zero in M0 3 in this
case — pO is pressed and the message
will be printed.

The program works by using

Indirect indirect addressing. This
simply means that each code number
sends the program pointer to a
specified memory, in which is stored
another 10-digh number. The
program reads this number and
splits it up into five two-digit

columns of seven rows — a five-by-
seven matrix for each letter.

As an example, let us take the
letter H. The code number under
this scheme is simply 08 — the
eighth letter of the alphabet. The
program now looks for the indirect
address, code number +43, which is
memory 51 in this case. The
memory list shows that M51
contains the number 40.10101040.

The first two digits are split off by
the use of the INT function in the
program, leading to the indirect
address of M40. This memory
contains seven ones and is thus
printed as a full vertical line.

M70 for a large space. It should be
noted that if wc worked with 3
smaller matrix, say, five by six, there
would be no need for codes greater
than 63 (2* — I) and we could simply
use one series of indirect addressing
instead of two.

If you own a Micro and spend
much of your time using machine
code you will find the following
program from Brendan Kelly of
Nottingham most useful. It is
a simple program for the Casio
FX-3500P to convert to or from any
numerical base, he writes. I found it
particularly useful while developing
machine-code routines for a TRS-80

Sharp's PC- J 500 band held computer with

numbers. Each of these is inter-
preted as the indirect address for yet
another memory which will contain
seven digits: either a or a I.

Finally, these seven digits are
printed as a column with a zero rep-
resenting a blank and a one repre-
senting a block. Hence each code
number is interpreted as five

four- colour printer — is this the right kind of progress?

Similarly, the next two digits are
split off

tNT(l00xFRAC(M51IJ
and lead to the memory location
containing 0.001000, It is now trans-
parent that wc will be forming a
letter of the form shown in figure 1 ,
The character codes are stored in
the 27 memories from M44 for A to

Program fist

Memory list.

K88-79,F-&F i84ste?s

H68-Te?F-6F 184sief5

R15*

8.011

L3L5

l\i*

8, 8 11881

*** ?9

HR3F FRflC x 18 =

K88=-25.1521i02?

fii?=

6.8111

i */- HinF

His3F 60I03

S81= 3.15:::.

K13=

e.einii

LBL9

LBL7

H82= 20.0510

m*

8.:

i m

7

H83= 8.

-.: =

8,

m W x=8 60TQ8

SAVE invEXE

*84= o.

HinlF

HR2F FRfiC x 188 =

?85= i.E-06

828=

0.18888!

LBU

Hift2F x=8 60TD8

<§&= i.E-05

H2i=

8.1839:

43 H+1F

80102

$87= i.lE-05

«22=

8. 18811

!HD KR1F Uffi

LBL8

«80= I. £-84

nur

8,181881

L8L2

- ft

m-- l.iE-84

m-

8. i 1811

IN* HR2F Hin3f

SfiVt invEft

R0F= 3.

*25=

8. H181

LBL3

URi? 'RfiC x 100 =

K26=

8.11111

8R3F x=8 B0TO7

niniF mmm

«27=

8.H1111

IHT x=8 S0TG4

son ■

Hits i.88iE-83

«28=

1.

«. n »

tao

ni2= i.iE-03

*23=

1.888881

60705

•««095steps

Vii- o.8i

w--

6.

L8L4

814= 8,8181

(listing continuec

J on next page/

to which I had limited access and no

assembler.
The best way to initialise the

program is to kev in the following:
MODE Kin 5

INV KAC 0.499999999

1 Kin 6
Kin 3 INV PCL

2 MODE 7
Kin 4 PI

10
Then key in the program itself:

Kin 1

X

—

Kout 3

Kout 4

=

Km- 1

Kin -2

Kout 6

Kout 5

Kin !

KinX3

Kout 1

Kout 1

(NV RND

INVXM)

Kin 1

1

X

Kin 3

Kout 4

Kout 2

m

Kin -2

Ixavc LRN mode:
MODE*
As initialised, pressing PI will
f continued on next page/

Figure I

10001
1 0001
1 0001
11111
1 0001
10001
10001

or, more clearly

YOUR COMPUTER. JUNE 1982 63

FINGERTIPS.

Sample printout actual size - from Casio program.

(continued from previous page}
cause the displayed number 10 be
converted 10 binary. For example,
enter 25, press Pi and after a short
pause 11001 will be displayed. The
program can then be reused by again
pressing PI: reinitialisation is only
necessary if the calculator is
switched off when Mode 7 will
have to be re-entered or if the con-
tents of Kl to K6 are inadvertently
changed when the values will have to
be re-entered.

Obviously, conversion to bases
greater than 10, e.g., hexadecimal,
cannot be carried out so simply as
each digit of the required base, i.e.,
nybble, will have to be represented
by more than one digit of the
display.

For example, as the FX-3500P has
a purely numerical display, each
nybble of hexadecimal will have to
be displayed by two digits. Thus
3CFOH 'would be displayed as
3121500 which could mentally and
at a glance be recognised as 3 12 1 5 00
and if necessary to 1 5 could be
replaced by to F.

To accommodate this method of
display not only must the base to
which we are converting be stored in
K4, but 10° must be stored in K5
where n is the number of display
digits required per digit of the
specified base.

The contents of K4 and K5 for

conversion to useful bases can be
summarised:

Binary Hexadecimal Base 256
K4 2 16 256

K5 10 100 1000

Conversion to base 256 is useful
for splitting addresses into their
least- and most-significant bytes. For
example, 32767 will be converted to
127255.

The main point not so far covered
is conversion from rather than to a
specified base. This could hardly be
simplier and is accommodated by
exchanging the contents of K4 and
K 5. This should cause no added dif-
ficulty as long as the strict format of
entry is adhered to. That is, 3CFO
hexadecimal must be entered as
3121500 not 312150, and 64 base
256 must be entered as 64000.

Once this program is understood it
can be simply adapted for almost any
programmable calculator which uses
an algebraic hierarchy, has at least
six memories and a conditional
jump. The instructions which may
require explanation arc:
Kin 4 store in memory 4.

Kout 4 recall in memory 4.
Kin + 2 Sum to in memory 2.
1NV X>0 return if x, the display, is

greater than to the first

program.
PI causes execution from the

first program step.
INV RND rounds the internally

stored number to that

displayed — fixed to
decimal places.
A simple, but pleasing, timing pro-
gram for the Sinclair Enterprise Pro-
grammable comes from John Lewis
of Llanelli. This is a much shorter
program than is supplied in the
Sinclair applications books, he
writes. When run, it will time
accurately over long or short period
timings, giving a readout in seconds.
Before each run, you should first
key in Sto 0. This sets the timer to
zero, as subsequent readings will be
stored in Mem 0. Again, after each
run, RCL should be keyed in to
provide a reading in seconds.
Pre-execution; STO

KEY STEP

- /EE 01

2 02

6 03

M+ 04

05

GOTO oe

07

i oa

Post-execution: RCL

Finally, Douglas McGibbon of
Edinburgh writes in with two short
points on the HP-41C. He writes:
the first item is a small program
designed to eliminate the laborious
task of manually deleting various
memory registers when you cannot
use the CLRG function because you
want to keep some of the registers
intact.

(listing continued from previous pagel

r!38=

1*088811

848= 1.111111

W*

26.29333325

868=

26.29342835

m*

1. 383181

H41= 8.11881

H51=

48.1818184

H61=

48.11162332

i. 83811

842= 8.

H52=

4.29482584

22.33333341

ft33=

i. 081881

H43= 8.

H53=

19.28292785

R63 =

5,85488585

R34=

1.813881

?i44= 39.11111139

H54=

48*11142129

H64=

27.28282827

H35=

1. 61111

H45= 48.33333324

43.28282823

R65=

13.19281518

m=

1.16888!

m= 26. 29292921

"56=

48.8612864

K66=

48.1915194

R37=

1.188811

*47= 48.292:2117

K5?=

48.8818134

H67=

838=

1.111

K48= 48.3333332?

H58=

26.29292926

m=

7.88388897

H33=

i.lllll

W* 48.11111185

H5S=

48.11111189'

H69=

83F=

H4F= 8.

H5F=

8.

B6F=
878=

8,

4.84848484

The program itself only occupies
24 bytes of memory space and uses
the X and Y stacks to hold the limits
of the memory clear. Once the pro-
gram has been loaded and assigned
to a key, all that need be done is to
enter the upper limit of the memory
wipe into the Y stack and the lower
bound into the X stack and then
execute the program. For example,

8ENTER3R/S
will delete registers 3 to 8 inclusive.

01 LBLaMOPa

02 LBL 00

03 STO IND X

04 ST IND X

05 X = Y?

06 STOP

07 1

08 +
09GTO00
10 END

Secondly, in the manual it is stated
that memory modules should always
be inserted in the correct order* so I
moved my sole memory module
from port 1 to port 2. After a little
experimentation I discovered that I
had a block of memory that could be
used as memory registers only and
not as program registers.

As to be expected these registers
were numbered in the conventional
pattern as if there was a module in
port 1 also. That is, from a cold start
with a module in port two, the new
block of registers is numbered 81 to
144. The most interesting finding
was that although the statistical
registers can be assigned to this
block, the shifted set of registers is
not affected by the CLRG function.
This provides another use for my
program.

This immunity is apparently
because of the fact that when the
CLRG function is executed, the cal-
culator only checks the first port for
extra modules. On finding none, it
assumes no extra modules are
plugged in and stops where it is. It is
also possible to store something in a
register, move the module to a dif-
ferent port and recall it by using the
new register number.

64 YOUR COMPUTER, JUNE 1982

SPOCK: "Computer" Calculate the value of Pi to ten thousand d**cimal places'*
COMPUTER* "Working "

CAN YOUR COMPUTER SPEAK?

The WIDEBAND SPEAKEASY speech synthesiser adds voice
response to any computer with a parallel port including PET,
APPLE, expanded ATOM, HORIZON etc.

for Only £69 - vat

* UNLIMITED VOCABULARY

*• EASY TO PROGRAM

•>r LOW MEMORY OVERHEAD

*r COMPLETE MANUAL WITH
DICTIONARY, SAMPLE
SOFTWARE AND TUTORIAL
ON SPEECH PRODUCTION.

Also includes high Dux speaker and power fupply, *U housed m high quality wood
cabinet with volume control and rear pitch control

Programmed with simple phonetic codes Apert from the obvious applications of
voice response in manufaenmAg. testing, blind terminals etc. tlus product also
teaches a o*eat deal about Un^uisncs and speech production.

Sofrwaxe is available in BASIC and 2-dO ard 6502 assembly for direct input in
PHONETIC SPELLINC ck**iy related to the ARPABET iniemanonal phonetK: alphabet.

For your nearest dealer contact:

UHOEBUftU,

ORWELL. ROYSTON, HERTS TEL0223 208017

A subsidiary of Sands-Whtteley Research and Development

PRODUCTS, CAMBRIDGE RD,.

SOFTWARE

for ZH-81QK & 16K) or BBC CUcro

New maths programs - improve your maths and
programming skills by playing Simon maths Games

Choose your own level of difficulty -suit ages 10-16.

10 programs on each tape - most incorporate Moving
Graphics and are fun to run.

Let your computer help you to pass your exams

Maths 1 Number, Area. Fractions. Decimals, Money Length.
Number Estimation, Test 1; Came 1 .

Maths 2 Volume, Ratio, Percentages, Perimeter Bases Jime,
Number Estimation, Test 2, Came 2

Maths 3 Directed Number Co-ordinates, Angles, Scale, Probability,
Density Temperature, Estimation. Test 3, Game 3

Maths 4 Sauare Roots, indices. Circles, inequalities, Statistics,
Number Fractions, Angles Jest 4, Came 4

Maths 5 Equations, Directed Number. Statistics, "
Probability. Circles. Equations, Pythagoras,
Simultaneous Equations, Test 5, Game 5

Simon Software

Quality tapes copied at normal speed for
better reproduction

Cassettes £4 each (inc. VAT).

Printed Programs £1 (inc VAT).

Please add £i p&p

FREE! blan'< tape with each set ordered

Send cheque/POto Simon Software.
Freepost New End, Redditch
(State ZX-8K1KM16K) or BBC)

ZX81 HARDWARE

40 KEY KEYBOARD Kit C20.95. Built f25 7$ fRETO

• Proper Typewriter style keys.

• All legends and graphics in two colours.

• No soioerinq required to 2X81 Ptups in.
< RAM /Primer not affected \

• Complete with aM parts, connector 'eat & n & comprehensive instructions.

24 LINE IN/OUT PORT. Kit £16.95. Built €18.95 (RE98)

• Each tme either in or out.

• Controlled by BASIC.

• Aflows printer/ RAM to be used without a motherboard.
(Motherboard version kit £13.50. Built £14.50*

3 CHANNEL SOUND/TIMER BOARD. Kit £16.95. Built £ia.&5 <R£i6ii

• 3 independent channels.

• Controlled by BASIC.

• fu I range of notes.

'• Complete instructions with examples provided,
e Can be used as a sophisticated timer /counter,

MOTHERBOARD. Kit £15.75. Built £18.50 IRE82)

• Two connectors on board,

• Six connector board. TBA.

CONNECTORS & PLUGS

• 23 Way female connector for 2X80/81 . (RE80) £2.95.

• 23 Way mate connector (RE87J £1.30

• 23 Way male connector to fit two female connectors together. {RE90> f 1.60-

• 30 Way ribbon cabJe. £1 .40 metre

• RAM pack connector. Allows RAM pack to be remote from ZX80>'81
RE170 £6.95 built

• In 'out connector and sound board connector. (RE7$8» £2.95.

BOOKS AND TAPES

Getting acquainted with 2X81. £4.95.
Mastering machine code £5.95
Programming for real applications, £6.95.
Tape fof real applications book. €11 44

Send SAE 5" x 7" for free illustrated catalogue.

Alt products available ex stock (allow 7 days extra for built products.

PAYMENTS: Cash with order or ACCESS/BARCLAYCARO. Ofttr.al order welcome.
Dealer* write for rates

AH prices include p&p and VAT. Overseas add £1.80.

REDDITCH ELECTRONICS, DEPT. YC

21 Ferney Hill Ave., Redditch, Worcs. B97 4RU
Tel (0527) 61240.

ZX81 BLEEP

Wouldn't it be great if your keyboard provided some sort of
feedback to let you know whether or not you had pressed the
right spot hard enough?

Ordinary keyboards provide this feedback by means of
mechanical movement, but of course this is lacking in your
touch keyboard, hence you need constantly to refer to the
screen to check that each item typed is present and correct.
The ZX81 Bleep provides a short audible sound as feedback,
thus typing programs takes less time and involves fewer errors.

We have kept the installation as simple as possible. Afo
soldering is necessary; this means that 12 infrequently used
characters (out of a total of 210) do not bleep. In practice this
tends not to be a problem unless of course you plan to make
frequent use of such characters as inverse £!

You can easily fit the bleep inside your ZX81 in a matter of
minutes using only a screwdriver Everything else is provided
including full installation instructions.

Ready assembled and *ully tested only £9.95.
Kit form only £7.95. Prices include post and packing.

FULCRUM PRODUCTS

HILLSIDE, STEEP LANE, RNDON, WORTHING,
WEST SUSSEX B.M14 0UF

YOUR COMPUTER, JUNE 1982 66

KUCEUJKIflHE

RETAIL SHOP IN

LEICESTER
for ZX81

ACCESSORIES, SOFTWARE

Keyboards, Ram Packs, t/O Ports, Monitors, Graphic
Bom; Home /Business, Educational, Serious, Games
Programs; Books, etc.

* SPECIAL AT ZX MICROFAIR *

S/HAND SINCLAIR MACHINES e.g. ZX81's £47.50

also

NEW SPACE-TYPE GAME BY COLLINS

COMPUTING

ORIGINAL GAMES, ENHANCED MOON LANDER

ETC BY COWIE COMPUTING

DORIC COMPUTER SERVICES "ORACLES CAVE"

SCISOFT ORIGINAL EDUCATIONAL PROGS &

"TEACHERS MARK BOOK"

+

'A' LEVEL/TECHNICAL PROGS BY COMPUTER

TRAINING CONSULTANTS

BYG-BYTE 16K RAM PACK, ETC.

MJCRDKIflRE

131 MELTON ROAD, LEICESTER
TEL: LEICS 681812

(OPEN 9.30-5.30 - CLOSED THURS, SUNDAY

33

m

MJCRQKIflflE

a*T?Z] MEMORIES
aXJJ with a DIFFERENCE

A^CLNONG THE END OF THE ROPPV ft AM PACK' Now. f<>' the t.r*i t *rm.
alt yOu need CO M up to a foil 5$K of tow pow*f memory INSIDE vow ZX8T (at it
narmjf wtm rnort t *pt<wv« personal eo/npuTers), •* a $ef*worrver Experience K»*
*howrt tHat tr** two cOflv*x>rte*t closes of ZX81 memory add on failure ore

1 Lock of ripditv m th« conrtaetion to tho *«p*n*o<t pon.

2 ^*c>Quaie regulated power *upptv.

Both th«* protterm have &e*« overcome with our iow-oow*» inter r**lry fitting
INCftEWENTAl arwJ MAXIMUM mittnow

INCREMENTAL 1.2

The ■jr^ly #«;u!vJ.ib> memory «y«em ihai 41am vou off at a pro© vow cart ***ord but

pittas no r#*tr*:ton% or your future expansion

• EASY TO *rT The ofNfluefv dc*««*d boa-d plugs »:?*flM In to the ete-iino.
nx*opfoce*4o* lCPU3 sockti oo 2X31 board (See paoa 162 o! 2XS1 manual «o,
lotowtg the m*truewt* provided, you *mpV open up the 2X61 cave, unplug th«
CPU and plug rt into :he memory board, then plug the memory board into foe
vacant CPU socket. Four additional b©H» fit through c*»t.r>g ho tea »n 2X81 board
to O've h»oh rio«d*ty retvabifcv . S»mp»e to follow m*if ucttom maket cwd* piay o'

a (and removingt

• TRULY EXPANDABLE - E^parKlaWe op to 16K byte* *i ntCtement* of 2K *-rtp*v
by plugging *i memory chip* but does not itop thera 1 Plug And aodkai switch**
aaow running tn conjunction with external memory add on$ c y with S'ncia*"
16K RAM pack to gn* up to 32K and win 32K and 48K packs to ftive up to 48K
ana 96K <mex poss) retptctrvety. Fun -muucikxn provided.

• ULTRA LOW POWER A *u» 16X takes typ<afy lass power than ex* t^o, IK
Sinclair RAM (about 40mat

• ECONOMICAL - inctmaintal 1-2 with on* 2K crup giving 3K of RAM costs onry
f 16.43 (plus VAT> »nd you won't have to throw it away when you want more
mt rncey,

• MONEY BACK GUARANTEE - Return witnm 14 days Of recent secures ful
refund of p*ice of goods.

MAXIMEM 1.1 - NEW LOW PRICE

The 2XS1 mtcraproeassor can address a maximum of £SK of memory oVcctfy. More
than trns would require frequent adddfonal statements tn programs to twitch between
different memory banks. BK of this q&K •$ already taken up by the Ssnciair ROM
(containing the Operating system program and Bas*c interpret rJ thus iaavutg a
maximum RAM capaoty of S6K l - &4k-3k.i. The MAXIMEM 1.1 atw-ns th* upper
limit in one bound by ut Using the latest »n high density, ultrj tow pewor* memory
Board design is Simlar and fitting identical to the Incremental memory described

above.

Orders and energies to: East London Robotics. Finland* House. 14 Oarwell
Close. East Ham, London E64BT. Or cat us on 01 471 330t,

Quantity item

ORDER FORM

Price per item Total

Incremental * 2 socketed for max o! eX £ 10.50

increments! * .2 socketed fo* max o* 16K CI '.50

2K CMbS HM 6116 P-3 memory chips t*M

M»*im#m 1 1 5CK marrory £73.50

( \5% VAT

TOTAL

NOTE: Postage 46p for ofdefs und*f £15

I enclose a cheque 'postal order payable to East London Robotics for t_

Name*., .

AiV>««-

ZX81 USERS!

We are not tho first, but we think we are the best, because we have toarnt from the
problems of others.

EVEN MORE MEMORY

16K RAM PACK FOR SINCLAIR ZX&1

• LIES FLAT — no losing your program at the crucial moment.

• FULL ADDRESS DECODING - map* into any 16K block.

• Uses LOW POWER DYNAMIC RAM with on board refresh circuitry.

• Plucjs into ZX81 o r mounts onto our EXPANSION MOTHERBOARD to give up to
64K of RAM.

• £29.50 + VAT (Total C33.93J

EXPANSION MOTHERBOARD

• FIVE buffered slots plus SINCLAIR edge connector.

• LEOs to monitor Software and Hardware operation.

• ADDITIONAL ADDRESS DECODER to correct Sinclair 'Reflection' problem - full
64 K available for RAM /ROM addressing.

• RESET BUTTON to ctear memory below RAMTOP without power- down.

• REGULATOR (1 amp 5 voUJ for optional extra power supply.

• Can be chained.

• BANK SWITCHING - allows use of SINCLAIR ROM
Monitor /Interpreter area modify them to suit your needs.

• W»de range of PLUG IN CARDS under development (includes EPROM BOARD) -
SERIAL PARALLEL INTERFACE 16K RAMPACKS available now.

• Optional METAL CASE.

• EVEN MORE EXTRAS - wo haven't the space to describe
write for full specification

• £34.95 incl. VAT
CASSETTE INTERFACE

• HAVING TROUBLE LOADING?

• interface your ZX81 through this interface and overcome these problems,

• £8 + VAT (total £9.20)

COMING SOON

MINI EXPANSION MOTHERBOARD

• 3 slots

• USE TWO RAM PACKS and INTERFACE CARD

• COST about £10

SERIAL PARALLEL INTERFACE CARD

• CENTRONICS - compatible ParaHel Interface

• RS232 Senal Interface

NOW YOU CAN USE ANY REGULAR PRINTER with your ZX81. connect up to a

modem, speak up to other computers etc.

Aff prices include P&P

Write for details or see us at ALCC London Computer Fair

Earls Court

ZX8I Mtcrofair

CAPITAL COMPUTERS

Head Office: 100 Church Street LUTON
Technical/Sates: 1 BRANCH RD. PARK ST. ST ALBANS. HERTS

(0727 72917)

ZX81

ECONOMIC KEYBOARD

£11.95

Would you like an easy keyboard to use? Would you
rather not pay £30 or so to get one? What you need is
A SINCLAIR USER'S ANSWER
TO A SINCLAIR USER'S PROBLEM
simple, straightforward, utterly reliable.

It is NOT a full-sized typewriter keyboard with full-travel
keys to be wired up in some way to your computer. You
don't need that.

IT IS:
SIMPLICITY ITSELF TO ATTACH fitting directly over

Sinclair's flat keyboard
NEAT AND UNOBTRUSIVE, in no way interfering

with any other expansion
SURE IN KEYSTROKE
FAST AND EASY TO OPERATE
ATTRACTIVE TO LOOK AT

IT HAS:
A SLIM BLACK BOARD with
ENLARGED AND RAISED KEYS which are
COLOUR-CODED AND EASY TO READ, and offers
SWIFT LOCATION OF FUNCTIONS etc

MAKE YOUR ZX81 A REAL PLEASURE TO USE
Send cheque IP. O. for €1 1.95 to:

DAVID HEARTFORD
91, High Street Evesham, Worcs. WR11 4DT

66 YOUR COMPUTER, JUNE 1982

SOFTWARE FILE

Software File gives you the opportunity to have your programs, ideas
or discoveries published. We will accept contributions for any
personal computer and will group programs for like machines
together in the file. Please double-check your listings before sending
them, and specify the memory they require. Mark your letter clearly
for Your Computer. We will pay £6 for each contribution published.

Code transfer

Nick Goodwin,

Eyemouth,

Berwickshire.

32~ffl

If YOU ARE experimenting with machine-code
programming on the ZX-81 the moment will
arrive when you want to incorporate a
machine-code routine, which you have in one
program, into another program. This can
present a problem, since machine codes arc
often long and laborious to enter. The follow-
ing process, however, enables machine code to
be transferred from one program to another
with a minimum of effort, and error-free.

First, RAMtop must be set at some conven-
ient level. I generally set it at 32000 for this
kind of work, which gives 768 bytes to play
with, while leaving well over 15K for Basic
listing, display file and variables.

The following routine enables RAMtop to
be set easily at any desired level:

10 INPUT X
20 LET Y = INT(X/256)
30 LETX = X 256* Y
40 POKE 16388.X
50 POKE 16389,Y
60 NEW

Run the program, enter the number to set
RAMtop, press Newline. The program
promptly disappears — line 60. If you want to
check that you have set RAMtop correctly, the

Peek at Pokes

S J Ridgway,

Wheathampstead,

Hertfordshire.

m^&d

I OWN A Vic-20 but I have used a Pet before, so
I have many programs for the Pet. The main
problem with converting Pet programs to Vic
are the Poke numbers. So I have made a list
that I think will be very useful to many Vie
owners which shows the Pet's Poke numbers
against the Vic's Poke numbers. The chart
also shows the Vic Poke numbers when your
machine has more than 8K of memory.

Test of character

Peter Vasey,
East Bofdon,
Tyne and Wean

A BRIEF EXPLORATION of the BBC Micro's
character set reveals no built-in graphic
characters other than some inverse spaces and
a weird set of characters which appear to be
concerned with controlling the teletext print-
out. For example ChrS(141) in conjunction
with a two-cycle For-Xext loop prints double-
height letters. For example:
10 MODE 7

following command will print the number you
entered:

PRINT PEEK 16388 + 256*PEEK 16389

Now load the program containing the
machine-code routine which you want to
isolate and transfer. I assume here that the
machine-code routine is stored in a Rem
statement in line 1, but the program can easily
be adapted by adjusting the initial value of J in
line 9030. This should be the address prior to
the address at which the machine-code routine
commences.

Add the following lines to your listing. I
have chosen to number them from 9000 but
that is not important — simply slot them in
where vou can.
9000 FAST
9010 LET RAMTOP - PEEK 16388 + 256* PEEK

16389
9020 LETX$ = ""
9030 LET J = 16513
9040 LETJ=J + 1

9050 IF PEEK J = 1 18 THEN GOTO 9080
9060 LET X$ = X$ + S TR$ PEEK J + "(inverse

space)"
9070 GOTO 9040
9080 FOR J = 1 TO LEN X$
9090 POKE RAMTOP + J, CODE X$(J)
9100 NEXT J
9110 STOP
RUN 9000

When that has finished a few seconds later,
load the program to which you wish to
transfer the machine-code routine. Again, I
assume that you want to Poke the routine into
a Rem statement in line I, but this can be

changed by altering the initialising value of J
at line 9010 to the address prior to that at
which you want the machine-code routine to
start.

First, you must reserve some space in the
normal way:

1 REM XXXXXXXXXXX . . .
Note that, using this routine, it is not critical
that you enter the correct number of Xs at the
first attempt. If you are short, the program
will stop and tell you, so you can add some
more. If you enter too many, it is a simple
matter to edit them out afterwards.
9000 FAST
9010 LET J = 16513

9020 LET R = PEEK 16388 + 256* PEEK 16389
9030 LETX$ = ""
9040 LET R = R + 1

9050 IF PEEK R = 128 THEN GOTO 9090
9060 IF PEEK R = 0THEN STOP
9070 LET X$ = X$+ CHR$ PEEK R
9080 GOTO 9040
9090 LET J=J-M
9095 LETX-VALX$
9100 IF PEEK J = 118 THEN GOTO 9130
9110 POKEJ,X
9120 GOTO 9030
9130 PRINT "INSUFFICIENT SPACE -

EXTEND LINE 1 THEN GOTO 9100"
9140 STOP

Run 9000, or Goto 9000 if you have data to
preserve. When it is done, List; there is your
machine-code routine safely lodged in line 1. If
you want to tidy the program, edit any surplus
Xs from the line.

You may be tempted to simplify this pro-
gram, by simply copying the Rem statement
data as it stands into a literal string and Poking
that over RAMtop. However, be warned; that
does not always work. Characters that are
printed as a ? in the Rem statement are
reduced to code 15, Thus, although the line
may look identical to the original, it will not,
in fact, work as a machine code.

PET MRPPING

VIC MRPPING

VIC COLOUR

VIC 8K+ MRP

VIC 8K+ COL

32768

- 32887

7680 -

7701

38400 -

38421

4096 -

4117

37888 -

37909

32898

- 32847

7702 -

7723

38422 -

38443

4118 -

4139

37918 -

37931

32848

- 32887

7724 -

7745

38444 -

38465

4140 -

4161

37932 -

37953

32888

- 32927

7746 -

7767

33466 -

33487

4162 -

4133

37954 -

37975

32928

- 32967

7768 -

7789

38488 -

38589

4184 *

4205

37976 -

37997

32968

- 33037

7790 -

7811

38510 -

38531

4206 -

4227

37998 -

38019

33088

- 33047

7812 -

7833

38532 -

38553

4228 -

4249

38820 -

38841

33048

- 33087

7834 -

7855

38554 -

38575

4250 -

4271

38042 -

38063

33088

- 33127

7856 -

7877

38576 -

38597

4272 -

4293

38064 -

:ses?

33128

- 33167

7878 -

7899

38598 -

38619

4294 -

4315

38086 -

38187

33168

- 33207

7900 -

7921

38628 -

38641

4316 -

4337

38108 -

38129

33208

- 33247

7922 -

7943

38642 -

38663

4338 -

4359

38130 -

38151

33248

- 33287

7944 -

7965

38664 -

38685

4360 -

4381

38152 -

38173

33288

- 33327

7$G6 -

7987

38666 -

38787

4382 -

4403

39174 -

38195

33328

- 33367

7988 -

8809

38708 -

38729

4404 -

4425

38196 -

38217

33368

- 33407

8010 -

8031

38730 -

38751

4426 -

4447

38218 -

38239

33408

- 33447

8032 -

8053

38752 -

38773

4448 -

4469

38240 -

38261

33448

- 33487

8054 -

8075

38774 -

38795

4470 -

4491

38262 -

38283

33488

- 33527

8876 -

8897

38796 -

38817

4492 -

4513

38284 -

38305

33528

- 33567

8898 -

8119

38818 -

38839

4514 -

4535

38306 -

38327

sT J v *T Z

~ 33607

8120 -

8141

38848 -

38861

4536 -

4557

38328 -

38349

33688

- 33647

8142 -

8163

38862 -

38883

4558 -

4579

38350 -

38371

33648

- 33687

8164 -

8185

38884 -

38905

4580 -

4681

38372 -

38393

33688

- 33727

33728

- 33767

20 FOR A% = 2 TO 3
30 PRINT TAB(5,A%) CHR$(141) "Hello"
40 NEXT

This is very useful for headings and titles.
Fortunately the provisional guide has a well-
documented section on the use of certain
aspects of the VDU command, including the
generation of special characters. The
command is VDU23,XXX s a,b,c,d,e,f > g,h
where XXX is the ChrS reference, normally

restricted between 224 and 255, and the rest of
the line is eight eight-bit bytes — the numbers
from to 255.

This very useful command can be pro-
grammed to generate any required character,
but unless one is very familiar with binary
numbers or has a full table of numbers from
to 255, the programming of each character
using graph paper can be very tedious. So I
(continued on page 69)

YOUR COMPUTER. JUNE 1982 67

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68 YOUR COMPUTER, JUNE 1982

(continued from page 67)
wrote this program to assist in designing
graphic characters. I have left in spaces and
not-used multi-statement lines in the interest
of clarity and readability, but approximately

SOFTWARE flLE

50 bytes can be saved by compressing the list-
ing.

Lines 40 and 50 set function keys and 1 to
these numbers to aid speed of entry of the
binary-number strings, and a character can be

entered in about 30 seconds. Line 220 enters
the character into memory and line 230 dis-
plays it. The correct VDU statement for
generation of the character in question is also
given — lines 250 to 290.

BBC CHARACTER SET

150

IF ASC<A$>=*49 THEN PRINT CHR#<240>; ELSE PRINT " M ;

ID DIN B<7>

160 fi*-RIGHT*(A*,AJO

28 @%=098010

170

NEXT

3© MODE 4

180

BCX>»A

40 *KEV0 e

190

PRINT A

58 *KEV1 1

200

NEXT X

60 CLS

210

*KEV1 RUN |n

70 PRINT TftB<5> -SPECIRL CHARACTER SET PROGRAM"

220

VDU23,250,B<0>,B<1>,B(2>,BC3>/B<4^,B<5>,B(6>/B<7>

80 PRINT '"Eisht x 8 diint Binary nos- are rehired. Use

230

PRINT "'Character is : ll ;CHR*C25©>

-function keys 8 and 1 -for inputs'"

240

&i=008001

90 FOR X*0TO?

250

PRINT '"Statement is • •'

180 input m

260

PRINT '"yDU23,XXX,".;

110 A*0

27©

FOR AX*0 TO 7

120 PRINT TBBa5,X+5);

288

print ecfijo;",";

130 FOR AK=? TO STEP-i

290

NEXT

140 ft«fi+C2*ftfO*:<fiSC<fl* >-4S>

300

PRINT' '"Press Function Key 1 to rerun"

m~83

Assault craft

C J Young,

Farnborough,

Hampshire.

THIS program for the 16K ZX-81 could be
easily converted to machine code, but the
Basic version is still very fast, very exciting
and flicker-free.

The program uses the full screen of 24 lines
of 32 columns as instructed in Timothy
Gilbert's February Software File article, by
Poking location 16418,0. It also uses the idea
expressed by Loll Holt in his November 1981,
Software File article on an efficient way to

move an object in two directions which is
shown in lines 270 and 280.

The aim of the game is to score as highly as
possible by destroying the alien ships which
travel along any of seven lanes. You have three
ships initially, only one of which is ever used
at the same time, and every time an alien
eludes you, one of your ships is lost.

However, you win a bonus ship when your
score exceeds 1,000 and other bonus ships
when you survive six attack phases. An attack
phase is eight alien ships and at the end of each
attack phase the lanes are reduced in length
which means you have less time to destroy the
ships.

Your score for the destruction of an alien is
calculated by how far along the lane the alien
was — the nearer to your ship, the lower the
score which can be obtained — and what
attack phase you are in.

You move your ship up and down by keys Q
and Z respectively with the firing of a missle
by key 0. You have one missile per alien.

Great care has been taken as to the screen
presentation with your spare ships indicated,
plus your score and attack phase. My high
score on this game was 6,060. As a piece of
advice, watch out for aliens on the last lane
because, for some unknown reason, they travel
approximately twice as fast as any other.

rx ASSAULT (J

10

LET P * e

2e

LET SC = ©

30

LET T - 3

40

POKE 16418,0

50

FOR A * O TO 19 STEP 3

€0

FOR B = IS TO STEP -2

TO

PRINT AT A,B; '•»*; AT A + 2, B; "*rf'

36

NEXT B

?0

PRINT AT A,26; ■ * "j TAB 26; ■ * "

100

NEXT A

ue

FOR A - 1 TO CT-I> * 2 STEP 2

120

PRINT AT A, 2S; ■■t'

130

NEXT ft

150

PRINT AT 23 > 6> •. ^Btf", AT 23, l6;
LET U * 1

■ 1.1.11. U

1£0

LET X »

iro

LET 5 - 10

180

LET H = -2

1*6

LET N « N ♦ 2

200

FOR A * 1 TO S

210

LET B = INT CRND * ?> * 3+1

220

FOR C = N TO 24 STEP 2
PRINT AT B,C; W

230

24©

IF X O THEN GOTO 510

250

IF INKEV* - "0" THEN GOTO 4S0

2£0

PRINT AT S, 22; " n

270

LET S = S + <<INKEV* - *Z n > *3> - <<INKEYf -

U Q*>*3)

280

LET S = S ♦ <<S - - 2> *3> - <<S * 22> $Z>

2*0

PRINT AT B, C; " % AT S, 22; '■'

3d©

NEXT C

310

PRINT AT U, 28; " "

320

LET U « U + 2

330

LET T * T - i

340

IF T * THEN 00T0 790

350

MgXT A

FOR A = TO 21

360

373

PRINT AT fi> N; " »

:-m

NEXT A

sc

3S5

PRINT AT 23, 12, N/2

390

IF NO 12 THEN GOTO 190

395

POKE 16418,2

400

CLS

41G

PRINT AT IB. fl: "| HfiU- flQN£, ATTACK HAVE DEFEATED I

428

PRINT "VOU GET A BONUS SHIP*

439

PRINT, , "HIT A KEY TO CONTINUE"

440

IF INKEV* =" " THEN GOTO 440

450

CLS

460

LET T « T + 1

470

POKE 16418,

4S0

GOTO 40

490

LET X - 22

500

LET SI - S

510

PRINT AT SI, X; " "

520

LET X = X - 2

530

IF X = N THEN GOTO 680

540

IF <X » C OR X ♦ 2 - C> PUD $1 = B THEN GOTO 570

550

PRINT AT SI, X; " - "

563

GOTO 260

570

LET X -

580

PRINT AT 31, C; -

590

LET SC - SC ♦ CN/2> « 10 ♦ (26 - C>

see

PRINT AT 23, 32; SC

610

IF SC > 1000 AND P » THEN GOTO 648

630

GOTO 350

640

POKE 16418,2

645

CLS

650

PRINT AT 19, 0, **LL DONE, VOUR SCORE MAS > 10O*

66Q

LET P » 1

670

GOTO 420

680

LET X *

690

GOTO 260

700

PRINT AT 10, 5; "ANOTHER GO?"

710

POKE 16418,2

729

IF INKEV* » -v* THEN GOTO 750

730

IF INKEV9 = -N" THEN STOP

740

GOTO 726

750

as

760

RUN

Pascal triangle

M R Tolun,
Canterbury,
Kent.

OfcB

-

Pascal triangle evaluates and prints several
rows of the well-known Pascal triangle. As a
reminder to those who are not familiar with
mathematical expansions, Pascal triangle is
simply formed of the coefficients of the

binomial expansion — that is, (l + x) n where
n=0,l,2,ete.

The triangle has a number of interesting
properties. First, it is symmetrical with respect
to its bisector. In other words, if you cut along
the central column, triangles on the left- and
right-hand sides contain the same terms.
Secondly, the sum of the squares of the terms
of any line is always equal to a number present
in the triangle. Thirdly, the sum of the
numbers in the nth Pascal line is equal to 2«.

When the program is run it produces a

numerical table, triangular in shape, in which
the sides are formed of unities. Any other
number is generated as the sum of two
numbers in the row above which are
positioned at the left- and right-hand sides
with respect to that number and this pro-
cedure is repeated for every pair of numbers
on the same line.

One advantage of the Pascal triangle is that

it can readily be employed in generating a

polynomial of nth order without actually

(continued on next page)

YOUR COMPUTER, JUNE 1982 69

(continued from previous page)
becoming involved in the difficulty of multi-
plying the appropriate coefficients. It is also
worthwhile pointing out that these coefficients

SOFTWARE FILE

arc formed according to the addition method
described and hence the complexity of
numerous multiplications is avoided.
Run the program and you can observe these

properties. For a IK machine the number of
rows should not exceed eight. With the
expanded memory? it is not advisable to go
beyond 54 rows.

PASCAL TRIANGLE

110 PRINT "PASCAL TRIANGLE :-"

120 PRINT

10 LET N=9

130 FOR 1=1 TO N

20 DIM PCN/N)

140 IF 1*6 THEN GOTO 170

30 FOR 1=1 TO H

150 PRINT TAB 14-1;

40 FOR J=l TO I

lbtf GOTO ISO

59 IF J=l OR J=I THEN GOTO SO

170 PRINT AT 1+2; 14-1;

60 LET P(I,J)=P(HJ-1) + P<I-1,J>

ISO FOR J-l TO I

70 GOTO 90

190 PRINT P(LJ).i" ";

88 LET P<I,.T>=1

200 NEXT J

90 NEXT J

210 NEXT I

100 NEXT I

220 STOP

Memory table

Gwyneth Pettit,

Otley,

West Yorkshire.

THOSE who have received their BBC Micro
may find the lack of explicit machine-code
facilities a hindrance in developing machine*
code routines. This program will tabulate an
area of memory, giving addresses and contents
in hexadecimal, which is also useful for eaves-
dropping on the Basic interpreter and the
machine-operating system. If decimal output
is required, the symbol ~~ can be deleted from
lines containing the Print statements.

10 INPUT "Start address "S%

20 INPUT "Finish address "F%

30 @% = 8020004

40 PRINT '"Hex'""Addre$s"

50 IF S%MOD8<>0 PRINT '~S%" ";

60 REPEAT

70 IF S%MOD8 = PRINT'-S%" ";

80 PRINT- ?S%;

90 S% = S% + 1
100 UNTIL S%>F%
110 PRINT
120 END

The symbol * may be unfamiliar to Basic users
— it forces output of a carriage return in BBC
Basic; & prefixes a hexadecimal constant, @%
controls output format and ~ forces hexa-
decimal format in printing. The ? in line 80 is
the BBC equivalent of Peek. For the purist, no
check is made on P% being larger than S% on
input, but our working version, which
includes hexadecimal input, hexadecimal
options and full error checking, is rather long.

Organic tunes

G N Owen,
Leamington Spa,
Warwickshire.

m^o

THIS PROGRAM for the ZX-81 enables the

>RUN

Start ,

address

3584

Fini sh

add

Iress

. 3781

EOO

D

A

1A

20

E8

22

53

E08

74

61

72

74

20

61

64

64

El©

72

65

73

73

20

22

53

25

E18

20

20

D

14

1A

20

E8

E20

20

22

46

69

6E

69

73

68

E28

20

61

64

64

72

65

73

73

E30

20

22

46

25

D

IE

F

E38

20

40

25

3D

26

30

32

30

E40

30

30

34

D

O

28

17

20

E48

Fl

20

27

22

48

65

78

22

E50

27

22

41

64

64

72

65

73

E58

73

22

D

32

19

20

E7

E60

20

53

25

83

38

3C

3E

30

E68

20

Fl

27

7E

53

25

22

20

E70

20

22

3B

D

3C

6

20

E78

F5

D

46

18

20

E7

20

E80

53

25

83

38

3D

30

20

Fl

E88

27

7E

53

25

22

20

20

22

E90

3B

D

50

E

20

20

20

E98

20

Fl

7E

3F

53

25

3B

D

EAO

5A

C

20

53

25

3D

53

EA8

25

2B

31

D

64

C

20

EBO

FD

20

53

25

3E

46

25

D

EB8

6E

6

20

Fl

D

78

ECO

6

20

EO

D

FF

20

This is a

tabu

1 at ion o

f th

e pr

ogram given

above.

From this

it is possible t

o work out the

way the

E» • B m C »

BASIC i

nterpret

er works

■

computer to function as an electronic organ.
The sound produced can be heard using your
cassette recorder's monitor facility or by
turning the TV's volume up and tuning it
slightly off the normal setting.

When Run pressing 1 sounds the highest
note and Y the lowest, although this can be

easily extended by adding lines 1700 onwards
and the appropriate lines 9041 to 9088. This
program occupies less than 2K.
Try this example tune

5.5.7-6-5-6— 7-8-8-9-8-7-9--
where the gap between each note represents
the duration of the note.

100

SLOW

291

GOTO 200

110

FAST

300

SLOW

190

IF IHKEV$0"1" THEN GOTO 9000

3 1 8

FAST

191

GOTO 100

390

IF INKEV$0 ,, 3"

THEN GOTO 9600

2@@

SLOW

391

GOTO 300

210

FAST

400

SLOW

2yy

IF INKEV*0 ,, 2" THEN GOTO 9000

410

FAST

70 YOUR COMPUTER, JUNE 198?

SOFTWARE me.

490

IF INKEV*0"4"

THEN

GOTO

9000

1210 FAST

491

GOTO 40U

1298 IF INKEV*0"W" THEN GOTO 9000

586

SLOW

1291 GOTO 1200

510

FAST

1300 SLOW

590

IF INKEV*<> ,, 5 M

THEN

GOTO

9088

1318 FAST

591

GOTO 508

1396 IF INKEV*0"E" THEN GOTO 9888

600

SLOW

1391 GOTO 1388

610

FAST

1400 SLOW

690

IF INKEV$0"6"

THEN

GOTO

9000

1418 FAST

691

GOTO 600

1496 IF INKEV*0"R" THEN GOTO 9800

700

SLOW

1491 GOTO 1400

710

FAST

1500 SLOW

790

IF INKEV*0 ,, 7 H

THEN

GOTO

9808

1510 FAST

791

GOTO 700

1598 IF INKEV*0"T" THEN GOTO 9008

S06

SLOW

1591 GOTO 1500

810

FAST

1680 SLOW

890

IF I HKEV.ro- "a"

THEN

GOTO

9080

1610 FAST

391

GOTO 3a@

1698 IF INKEV*0"V" THEN GOTO 9888

900

SLOW

1691 GOTO 1680

910

FAST

9000 LET I$=INKEY*

390

IF INKE't^O- 1 ^"

THEN

GOTO

9000

9010 IF 1*="" THEN GOTO 9888

99 IB GOTO 96

9820 LET V=l*a*="r , }+2*'::i$="2 ,, >

1086

SLOW

+3*a*="3"> +4*a*="4 ,, )+5*a*="5")

1010

FAST

+6*a$= ,, 6")+7*a$="7")

1090

IF INKEV*O U 0"

THEN

GOTO

9000

9838 LET V=V+8*a$="8") +9*a*="9")

1092

GOTO 1000

+i0*at-= ,, 0"}+ii*n$= ,, Q">+i2*a$="w ,, >

1100

SLOW

9640 LET , v , =V+13*a$="E"> + 14*<I*= ,, R ,, >

1110

FAST

+i5*a*= ,, T">+i6*a$= , "T ,,, >

1190

IF INKEV*0"Q"

THEN

GOTO

9000

9089 IF V=0 THEN GOTO 90OO

1191

GOTO 1100

989® GOTO 100*V

1200

SLOW

Deep-space attack

James Holland,

Stockport,

Cheshire.

im^mz

Space attack will run on a Sharp MZ-80K.
The instructions are contained in the
program. The Print €< C" in lines 2, 16, 43 and
50 is the clear-screen character. Usr(62) makes
a beep noise. The enemy is printed on the

screen in the following manner: |H^.

Lines 1 to 14 print the instructions.

Lines 15 to 23 set up the variables and print the

gun and enemy on the screen.
Lines 24 to 32 wait for instructions from you and

move the gun up and down.
Lines 33 to 36 count how many of the enemy

have passed you and position the enemy

randomly on the screen.
Line 37 produces a space* invader noise.
Lines 38 to 42 calculate if you have hit the enemy

— if you have, it blots it out — and adds it to

your score.

Lines 43 to 50 tell you how many of the enemy
you have destroyed and asks you whether you
want another go.

Here are some useful Pokes for the
MZ-80K. Poke 6637,80 disables the Break key
and Poke 6637,30 rc-cnables it. Poke 10680,1
makes a program unlistable and unsavcablc.
This can be cancelled by Poke 10680,0. Poke
59555,0 will blank the screen; Poke 59555, 1
will restore the video. Programs will run auto-
matically if, before saving, you enter Poke
10682,1.

SPACE ATTACK

3
4

c

G

10

11

12
13

14
15
lb
17
IS

REM COPVRIGHT ##*JflMES H0LLflND*#*<14>***

PRINT "C"

PRINT" C14 SPACES!? SPACE ATTACK"

PRINT" <14 SPACES)

PR I NT: PR I NT: PR I NT "The object of the same is to destroy as"

PRINT : PR I NT "many of the attacking fleet es you can"

PRINT: PR I NT "before -fi ye escape your fire."

8 PR I NT: PR I NT" REV':"
PRINT" <3 SPACES) H=so UK> <7 SPACES) Vour *un=<"
PRINT PRINT" <S SPACES) A=so down"

PR I NT: PR I NT" <y SPACES) S=F ire your aun <3 SPACES) The enemy =■■
PRINT: PRINT: PRINT: PRINT: PRINT" C8 SPACES) PRESS ANV KEV TO START"
USRC62)

GET A$:IF A$ "" THEN 14
USR-;b2)
PR I NT "C" :K=0
POKE 10167.. 1 : C=0

P=10

YOUR COMPUTER, JUNE 1982 71

SINCLAIR

ZX81 SOFTWARE

ZX 81 SOFTWARE

ALTERNATIVE PROGRAMS (M6K)

FOR THE MORE DISCERNING ENTHUSIAST!

CASSETTE 1
MATHS ONE t16KJ

ATTENTION ALL PARENTS! Prompted by an article in Practical Computing (Jan
81 J of inf error maths software, we decided to produce a program that would give
your child more than the boring reply: "sorry you are wrong, try again V*
MATHS ONE will give your child sums in the normal way and actually show your
child where he/she has gone wrong, Note the whole sum is printed on the screen
just as the child would do with pen and paper!
MATHSKATA (16)

Sec whose roilorskater can reach the post first but beware the sums become more
and more difficult! Maths one ■* Mathskate . . . f 335

CASSETTE 2

LANGUAGE TRANSLATOR

Having difficulty with foreign text? Then this is the program for you I Fast word for

word translation, from 600 words in seconds, Words car easily be changed and

SAVEd on tape. Please state language choice.

WORD TEST

For the very junior members of the family- WORD TEST will gfve Children partially

completed words. Second trys are allowed and the score out of ten with correct

answers are shown. Language Translator + Word Test . . . £3i>5

CASSETTE 3

BANK ACCOUNT (16KJ

Why wait for a statement when you can have your own personal banking system!

Accepts standing orders in the usual way and wiu tetl you when your balance is

below the free banking limit, then actually charge you for it! Just like the bank!

Statements can be backdated and up to 70 transactions can be stored l

HOME BILLS READY RECKONER

Want to know if your electricity /telephone /net pay are correct?

Bank Account 4 Ready Reckoner . . . €335

PLEASE MOTE: Our Software is of the very highest and stands to compare with

the very best from the Sinclair stable and even if we say so ourselves exceeds that

standard.

No kno wedge of computing required, just load and run I

YOUR ORDER IS RECEIVED AT 8,30 AND IS DESPATCHED BY 12,30 THE
SAME DAY. 14 DAY MONEY BACK GUARANTEE IF NOT SATISFIED + 6
MONTH REPLACEMENT GUARANTEE.

Make cwque$, PO, etc. payable to:

FUTURESOFT

38 PENSHURST ESTATE, PRINCE OF WALES ROAD. LONDON NWS

... is a stylish and
ergonomic plinth for the ZX81. It raises and tilts
the TV to avoid eyestrain, holds the 16K RAM in
place and hides the wiring and power supply.
This very professional unit costs £15, a built-in
power switch is £3, plus postage at £2.00, inc.
VAT.

Peter Furlong Products, Unit 5, South Coast Road
Industrial Estate, Peavehaven, Sussex BN9 SNA.

SOUNDwithZX 81!

MAKE AMAZING SOUND EFFECTS WITH
YOURZX-81

sfc

f

<?

£25.95 THEZONX-81

mclp&p&VAT

The Z0N X-81 SOUND UNIT is completely seff-contained and
especially designed for use with the ZX-81, If just plugs in -
no dismantling or soldering

No power pack, batteries, leads or other extras.

Manual Volume Control on panel - ample volume from built-in
loudspeaker.

» Standard ZX-81 - T6K Rampack or printer can be plugged into
Z0N X-Sl Sound Unit without affecting normal ZX-81 operation.

* Huge range of possible sounds for games or: Music,
Helicopters, Sci-Fi, Space invaders, Explosions, Gun-shots,
Drums, Planes, Losers, Organs, Bells, Tunes, Chords etc., or
whatever you devise!

* Uses 3-channel sound chip giving programme control of pitch,
volume of tones and noise, all with envelope control.

* Easily added to existing games or programmes using a few
simple "BASIC" lines.

FULL instructions with many exomples of how to obtain effects and the
programmes, supplied. Fully Guaranteed

GET SLANTED!

TOUGH
SMOKE
BROWN
PLASTIC

SPACE
ALLOWS
COOLING
AIR TO
CIRCULATE

MAKES YOUR ZX-81
EASIER TO SEE
EASIER TO USE

FIXED IN SECONDS WITH DOUBLE
SIDED STICKY PADS-SUPPLIED

*FREE*

Send cheque/cwo to:

ONLY £3.20

(includes VAT/P&P)

MAEILL ORDER MARKETING LTD

DEPT A SCHOFIELDS WAY,

BLOXHAM, BANBURY, OXON

72 YOUR COMPUTER, JUNE 1982

softwwb file.

19
20
21
22
23
24
25
26

28

2'3

3Q

31

32

33

34

35

36

37

33

39

40

41

42

43

44

45

46

47

48

49

5©

S=10

FOR T=2 TO 23

POKE 4466, S- POKE 4465, T- PRINT" m M m "

POKE 4466, P: POKE 4465, 25 : PR I NT" <"

V=0

GET fifi*

IF PEEK <1 7828 > =68 THEN V=-l

IF PEEK a 7828 > =65 THEN V=l

IF fifl*= M S" THEN 37

POKE 4466, P: POKE 4465, 25: PRINT" «

P=P+V

IF P=-l THEN P=0

IF P=23 THEN P=22

NEXT T

C=C+1

IF C=5 THEN GOTO 43

S=IHTC20*RNBCi>>*i

GuTO 20

FOR TT=1 TO 15: P0KE4514,TT ■ USRC68>*NEXT TT:USR(71>

IF P=S THEN 40

GOTO 24

POKE 4466, 3: POKE 4465, T •" PRINT" (5 SPACES)"

K=K+1

GOTO 35

PR INT "C"

PRINT: PRINT: PRINT = PRINT" <5 SPACES) VOU DESTROYED" ;K; " OF THE ENEMV"

TEMPO 4:r■1USIC"#BlRlR4Hl#fll-C:-flRl-H3-F3R5 ,,

PRINT: PRINT: PRINT : PR I NT "MOULD VOU LIKE ANOTHER GAME ?"

GET mnf Q*="V" THEN CLRvOOTQ 12

IF Q*="N" THEN 50

GOTO 47

PR I NT "C" :END

^Jti'MMJ

Reading speed

lain Weeks,

Prescot

Merseyside.

The PROGRAM, which is for a Microtan 65, is
a subroutine to add to a main program that
uses a large list of instructions — for example,
adventure-type games. The idea is to display
the instructions slowly on the screen at normal
reading speed.
The routine will function in its own right so

it is possible to see how it operates before
fitting it to a game. The routine can easily be
added to any program that uses instructions by
putting those instructions in the array H$(N)
where N — see line 10010 — is equal to the
number of array statements used. There are 10
in the case of my sample program. The line
lengths will have to be adjusted to suit
computers using a different screen format.

Make sure the main program does not con-
tain any variables H$(I) or N. If it does,
change the letters in the subroutine. Lines 1 1
to 13 are probably already in the main

program so just alter the instruction If AS ■
"Y" to suit.

Data statements would have been easier but
I decided not to use them for, if the main
program contains Data, then reading data
would require amending. The speed of the
printout is controlled by Line 1 1030 and Print
Chr$(12) is the clear-screen instruction on the
Microtan.

The program could be used as a reading aid
for youngsters, using a simple story and
gradually increasing the speed of printout as
the child becomes more proficient at reading.

PRINTOUT

1
Z
10

11

12
13

14
*+$$

ieeoo

1601©

10020
10030

(0040

REM M** PRINTOUT ♦♦♦♦

REM #♦ *Y IAIN WEEKS **

PRINT C*fc*<l2>

PfcINT*I>o «v **nt instructions <V/H> M

GET Bf

IF ft* *"Y" THEN OOSUB 10600

REM C0HT. WHIN PROG.

£HD

PRINT CHR*C12>

H -10:DIM H*(H>

H*C1> a 'This is a ct*»onstra±ion ot slow jftrintirv* to n»3*<* &***s

H*<2> ■" instructions nor* interesting and easier to r*2.&. The-

HS<3> * p o* the dispU* czn o* course be altera* by *obustin*

the"

16650 Hi<4> a'titin* loop. ■

16G60 HS<5> * M The addition of this routine to thecain i*ros<r*Ai is

IO070 HSC€> ■"matter of puttm* the instructions in a 'GOSUB' and"

10000 H*<?> »"assi*nin* each line to a 'DIM' array, then reading *ach

tetter-

10096 HSC8> » H of the array and Pi-intinn it out slowly."

101OO H*<9> =" Easy isn't, it"

10110 H*ae> »" fmd it looks flood!!"

11600 FOR I - 1 TO N

11010 FOR J - I TO LEN<HS<1>>

11020 PRIKT MIB$<K*a>.J,l>,

11030 FOR T «= 1 TO 50-HEXT T

11040 NEXT J- PR INT" ":MEXT I

11050 RETURN

Key to functions

C J Cattenach,

Welwyn,

Hertfordshire.

wfra®

The following tip allows one to use the
four functional keys on the right-hand side of
the Vic-20, These offer a total of eight

functions when used with the Shift control,
yet very little information is available on their
use. The users* hand-book, supplied with the
machine, simply says that these four tan
coloured keys may be assigned functions from
within the applications that you create, but no
detail is given to help the newcomer to the
machine who may be trying to learn Basic for
the first time.

10 GET A$

15 IFA$ = ""THEN 10

20 IF A$ = "tt" THEN PRINT 'THE USE OF

THESE BUTTONS IS EASY"
25 IF A$ = "f2" THEN PRINT "WHEN YOU

KNOW HOW"
30 IF A$ = "f3" THEN PRINT "AND THE

OTHERS"
35 IF A$ = "f4" THEN PRINT "ARE ALL

(continued on page 75)

YOUR COMPUTER, JUNE 1982 73

Keyboard with
Electronics
for ZX81

_..-..:_,._.

A fuil-size, futliravel 43 key keyboard that's simple to add to your ZXB1 and
requires no soldering in the ZX81.

Complete with the electronics to make "Shift Lock" "Function", and "Graphics 2"
single key selections making entry far easier.

towered from ZX8Vs own standard power supply -with special adaptor supplied.

Two-colour print for key caps.

Amazing low price only £19.95 ind. VAT and carriage. Order As LW72P

Full details in the June 1982 issue of "Electronics -The Maplin Magazine" on sale
at aB good newsagents price 60p. In case of difficulty send 60p to address below,
or £2.40 for annual subscription (4 issues).

impuni

Electronic Supplies Ltd

P.O. Box 3, Rayleigh, Essex SS68LR. Tel (0702) 552911

Retail shops at

159 King St., Hammersmith, London W6. Te* 01-748 0926
284 London Road, Westcliff-on-Sea, Essex. Tel (0702) 554000
(Shops closed Mondays*. All mail to Rayteigh address.

(>.*>.&• congratulates Clive on

Spectrum

We look forward to writing software for
Spectrum. Meanwhile we can offer:

BUSINESS GAMES ZX81

AUTOCHEF

As MD of a Catering Company you must negotiate for leases,
decide on menu prices, level of wages, advertising and dividends.
Each year you must predict the inflation rate. You are also given
options on consignments of wines and food and loan contracts.
You will be made to resign if you are not successful. There are 3
levels of difficulty.

AIRLINE

Can you compete with British Airways? You must decide on the
number of aircraft to operate, whether to buy or charter, whether
to enter into a loan or a fuel contrct and the levels of staffing and
maintenance. Problems encountered are tax demands, strikes,
cancelled flights, hijacks and aircraft crashes.

Both programs make use of HISTOGRAMS and BAR CHARTS

and show results in the form of Profit and Loss Accounts and

Balance Sheets. They use over 15K and listings are over 7 feet

long!

These games are simulations and data is therefore up to date and

realistic. Send £4.75 for one or £8,(X) for both.

Cases Computer Simulations, 14 Langton Way, London SE3 7TL.

Tel: 01-858 0763.

Whether you are a BBC Microcomputer owner, have
limited access or are merely interested, then LASER BUG
has something to offer you.

LASER BUG is an independent users group dedicated to
the support and enhancement of the BBC Microcomputer.

LASERBUG is a central point for ideas and information —
we want to hear from you and pass on your ideas and
discoveries. Write to us at the address below — but please
enclose a SAE if you want a reply.

LASERBUG newsletter is distributed to members each
month and is full of news, reviews, letters, articles,
programs, contacts and classifieds (rates on application).
Our regular meetings also go a long way to help you get the
best out of your BBC Microcomputer.

You want to join? for £12.00 you get a year's subscription
to LASERBUG, 12 issues of the newsletter and free entry
to all LASER BUG'S meetings and shows — or send £1 and
a large SAE (12" x 9") for a sample copy of the LASER-
BUG newsletter and all the latest information.

Write to:

LASERBUG

4 Station Bridge, Woodgrange Road,

Forest Gate, London E7 0IMF.

Microgame
Simultations

ZX81
16K

"2002" Navigate your space cruiser through the System of 100
Planets, trading, fighting alien patrols and coping with system
failures, gravity fields and the dreaded black hole. Your creepy
on-board computer, ZXAL, controls your routine systems but
beware — he may turn out to be a silicon psychopath.
Soccer Supremo Run your favourite club in your own style;
controlling game strategy, watching your team play other great
sides \n the Super League, transferring players, including star
names, making boardroom decisions or delegating to solve
business problems; improve facilities; spend gate money; lots
of the fun and headaches of the soccer boss's lifestyle,
includes graphics,

Battle of Britain As strategic commander of nine British
fighter squadrons you must track and intercept the devious
enemy bomber squadrons before they reach London. Micro
acts as a flight control and communications centre for patrols,
missions, intelligence reports etc. Sketch map provided. May
also be played on any map of SE England with a standard grid.
Kingdom of Nam As ruler of Nam you must control its
economy; allocating labour; building cities, factories and ships;
importing and exporting; negotiating pay claims and fighting
the looming threats of inflation, strikes, starvation, over-
population and revolution. How long can you stay in power?
Tycoon Start a company producing "widgets" and compete in
the market against a computer controlled rival. Start small and
build up your business or borrow money and start big. You
have to make decisions about financing, staffing, factory
space, machinery, pricing etc.

Asset Stripper Compete against your computer controlled
arch-rival "KO Investments"; capitalising companies on the
stock market, and bidding for takeovers to gain control of
lucrative assets. Can your micro really outwit you?
All programs 16K for 1 player.
£4.95 for 1/C8.90 any 2/£12.85:3/£16.80:/£20.75:5

Please sned cheque/ PO to: Microgams Simulations
73 The Broadway, Grantchester, Cambridge CB3 9NQ

74 YOUR COMPUTER, JUNE 1982

(continued from page 73)

USED IN THIS WAY/'
40 GOTO 10
45 END

Run and press Return. From now on, one can
enter the information by pressing the function
buttons, and without even having to press the

Multiplier effect

SOFTWARE FILE.

Raymond Lloyd Vickers,
Crewe,

mi

Developed on a 32K Pet, this program is
designed to teach students of economics the
concept of the multiplier.

The multiplier is, at its simplest, the effect
on the economy of a change in investment. For
example, if £1 million is invested in new
machinery, then the machinery makers receive
this sum, spend some of it and save the rest.
Those who benefit from the spending also
spend and save their income, so that the effect
of the initial investment is multiplied.

Technically, the multiplier is the reciprocal
of the marginal propensity to save (MPS)
which is itself defined as the proportion of any
increase in income which is saved. If the MPS
is 0.33 then, out of every extra £1 earned, 33p
is saved, 67p spent, and the multiplier is
1/0.33 = 3* So, every £1 investment will create
£3 worth of money income.

In the simple model, there is no government
sector so, no taxation and no foreign trade, all
investment immediately produces new output
in a 1:1 ratio. There is an initial limit of £3
million of productive capacity (P) while
National Income (Y) is also £3 million. The
MPS (S) is 0.333 so the multiplier is 3.

The initial level of investment in the
economy is £1 million. If the extra investment
causes money incomes to rise above the
economy's productive capacity then inflation
will occur, while too little investment will
cause a slump. The economic model and the
program are simple, but the program works
and can be used as a basis for more sophistic-
ated programs incorporating foreign trade,
investment lags, and so on.

Tape directory

5 Robinson,

Leeds,

Kent

ama

TYPE IN any program title in the list on the
screen, press Ncwline, start the tape recorder
playing and it will be loaded automatically for
you.

Return button. Line 15 ensures that the
pressing of any unassigncd buttons does not
have any effect.

One farther tip: Not all may be aware that
memory locations change as a result of insert-
ing a 16K memory expansion cartridge. This
is remedied by preceding one's program with

the short section of Basic code that follows.

2 SC = 7680 (Rem set screen for 5K or 8K)

3 CL = 38400 (Rem set colour for 5K or 8K>

4 FOR I = to 506

5 POKE SC + 1,160 H60 is a space)

6 POKE CL + 1,1 (1 colour white)

7 NEXT

SIMPLE MULTIPLIER PROGRAM

10 PR I NT" SIMPLE MULTIPLIER PROGRAM "

20 FRINfGNP IS 3 MILLION"

30 PR I NT "PRODUCT I ON IS 3 MILLIONS

46 PR I NT "CAPITAL OUTPUT RATIO IS 1 : 1 "

50 PR I NT "MULTIPLIER IS 3"

69 PRIHT"TRV TO ENSURE STABLE GROWTH"

61 PRINT" INPUT THE INVESTMENT V0U THINK"

62 PRINT"NECESSflRV. < MILLIONS) "

65 PRINT" VOU MUST INVEST AT LEAST $188*

70 V=3*10*6
88 P=3#10t6
98 1 = 1*101*6
100 S=0.333

118 INPUT flvfl-A*10t6

120 cv^a-A.vs

130 Vi=V-CV

if

Lf

i

140 PR I NT "NEW INCOME IS 1 ,r
150 P=P+fl

16© PR I NT "NEW PRODUCTION LEVEL IS" IP

180 IF V1>P GOTO 220

190 IF VKP GOTO 230

206 IF V1=P GOTO 218

218 PR I NT "GOOD. STABLE GROWTH"

215 GOTOllO

228 PRINT" INFLATION. DECREASE INVESTMENT"

225 GOTOllO

230 PR I NT "SLUMP. INCREASE INVESTMENT"

235 G0T011Q

REflDV

When you run the program you first input
the amount of programs you want on the list
— up to 16 with line 60 removed — then enter
all of those program titles. When you reach the
last title, start the tape recorder recording
before entering it. So, when you load Dir it
will run automatically.

When you Save the programs that are in the
directory on that tape, ensure that you save the
correct program name.

Cypher breaker

G L Billington,

Bebington,

WirraL

?Aot

THIS SHORT program, which runs in IK,
allows you to rapidly code or decode messages.
X at line 20 is the code number and shifts the
ZX code value of each character. The string
array at line 35 accepts the coded message.
Line 60 does the coding, while ignoring spaces
between words; line 65 keeps spaces, question

marks, commas and all full stops as they are.
To use the program, run it, and enter a
suitable value for X. To start with, try a value
between -1 and -9. Type in your message, but
remember it must not exceed one line of 32
characters due to the Dim statement at line 35,
Press Ncwline and in about five seconds the
coded message will appear on the screen. If
you have a printer, enter 00 and Newline to
escape from the program, and Copy. If not,
copy the coded characters by hand. For long
messages, this process may be repeated as
often as required.

D I RECTOR V

1

2

2©

30
46
50
60
70
30
90

100
110

120

130

REM DIRECTORY

INPUT A

INPUT B

PRINT" TAPE DIRECTORY "

DIM fi$<fl,EJ'

FOR 0=1 TO A

INPUT C*

LET A$<C)=C$

PRINT ,A$<C>

PRINT

NEXT C

PRINT" INPUT GAME "

SAVE "DIR "

INPUT H*

PRINT ..,,," START TAPE"

PAUSE 20

LOAD H*

To decode, give X the same value but of
opposite sign. If you have more memory than
IK, the program can be considerably refined.
As well as increasing the size of the array, the
code number X can be changed several times
(continued on page 76)

YOUR COMPUTER, JUNE 1962 75

SOFTWARE FILE

(continued from page 75}

during the encoding procedure. For example,
start with X= -8, then change it to say, -4 by
adding a line 58:

IF N>16 THEN LET X = -4
The basis of the code thus changes about half-
way through the line, making it more uncrack-
able. As long as the recipient of the message
knows the relevant numbers, decoding is no
problem.
Try using X = 160, and you will obtain a

Contents display

very interesting result indeed. When using

other values, check that characters are not

shifted into the unused range, or you will

obtain question marks which cannot be

decoded.

10 CLS

15 PRINT "CODE NO.?"

20 INPUT X

25 CLS

30 PRINT AT 0,0;X

35 DIM C$(32)

40 INPUT A$

45 IF A$ = *'0" THEN GOTO 10

50 IF A$ = "00" THEN STOP

55 FOR N = 1 TO LEN A$

60 IF A$(NK >" " THEN LET C$(N) = CHR$

(CODEA${N) + Xl
65 IF A$(N) = " " OR A$1N) ="?"

OR A${N) = "," OR A$(N) = "." THEN

LETC$(N) = A$(N)
70 NEXT N
75 PRINT
80 PRINT C$
85 GOTO 40

.£Bm

Gerard Leblanc,
Seraing,

Belgium.

This machine-code program displays the
contents of a cassette and allows you to tune
the cassette recorder better. Basic programs
saved on cassette can be viewed in the upper
half of the screen. This display can be stopped
at any time, by pressing any key except Brk,
Esc, shift and Ctl. It can be restarted in the
same way. Characters #00 to # IF are
displayed as inverted letters.

Line 35 clears the screen and line 36
requests you to have the cassette at the ready.
Press a key as for *Cat command. Line 40
reads a byte from cassette. Lines 45 to 75
convert ASCII characters to video code, put it
in the right position in video memory and
black out the 10 oldest bytes. Line 80 checks
for the key pressed to stop or restart the
display.

This program is executed by Link # 2800.
Another location could be used by changing
line 25 and the address in Link.

Artful dodge

DISPLflV ATOM

10

DIM NN<63

15

FOR 1-8 TO 6.;NN<I>= -1;N. I

28

P. $21

25

FOR 1=1 TO 2;P=#28O0

38 C

35

LUfi @#0;STfl #80;LDfl e#0C.;JSR #FFF4

36

JSR #FC33

40 : NN0

JSR #FBEE

45

CMP i#20;BCS NNi;fiDC @#B8:JMP NN3

58-NN1

52

CMP e#40.;ECC NN3;CMP @#5F;BCS NN2

54

SEC; SEC @#40;JMP NN3

60 - HN2

CMP e#E0;BCS NN3..BBC @#28

65 : NN3

LDX #S8.;STfl #8000,X.:INX.:LIfH @#C0;LBV @#8fi

70 •• NN4

STfl #S000,X,IHK;DEV,ENE NN4

75

LBX #80;1NX;GPX e#00;BCS NN5;LDtt @#80

80 = HNS

STX #30; JSR #FE7l;ECS HN6.:JSR #FE94

85 ■■ NN6

JMP NN0

90 Z3

100

NEXT I; P. $6; EWD

P Marco,
Romford,
Essex.

ART LETS you draw your own pictures on the
TV screen. Instead of the usual four directions
— up, down, left and right — this program has
eight directions. Not only can you draw
pictures but you can also rub them out.
The program starts in Draw mode. It can be

put into Rubout mode by pressing W. It can
be returned to Draw mode by pressing Q. The
directions are:
10 to 20 Starting place of blob.

30 Puts blob into "Draw" mode.
40 Checks for mode key.
50 to 80 Stops blob from leaving the screen.
90 Moves blob left and right.
100 Moves blob up and down.
110 to 140 Moves blob diagonally.
150 to 160 Blinks blob.

170 Gives Q Draw mode and W Rubout
mode.

180 Return to main loop.

The program wall fit into IK and a reason-
able picture can be obtained, A larger and
better picture can be obtained within the 16K
RAM pack fitted.

If you have a 16K RAM pack, you will be
able to save the picture on tape by deleting line
180 and adding these lines:
180 IF !NKEY$ = " " THEN SAVE INKEY$
190 GOTO 40

The picture will be saved under the letter
placed in between the inverted commas.

ie

LET

20

LET

3e

LET

40

IF

56

IF j

£8

IF

7©

IF

8©

IF

50

LET

x * 2S

v * 22

ftS = rt Q"
INKEY* ■ "Q" OR INKEVf = "M" THEN LET R* ■ INKEY*
x>= 60 THEN LET x - 60
*>* 40 THEN LET * = 46
x<* THEN LET x «
*<• © THEN LET *«e

x * x ♦ (INKEVf * "3"> - CINKEY* - "7">

£T * = * '
U0 LET x « x ■
120 LET * = *
130 LET x = x
140 LET * » v
150 PLOT x,v
160 UNPLOT xW
l?e IF R* * "Q
130 GOTO 49

ClNKEY*
<INKEY*

(INKEV*
UMKEV*
CINKEV*

-3">
l, 4".»

■2">

<INK£Y*
ONKEVf

ONKEVt
UHKEVS

"6*>

THEN PLOT x,y

Hex convert

Paul McGowan,

Atherton,

Manchester.

m=m

MY PROGRAM will be of interest to those who
have to use a hexadecimal loader. It simply
converts hexadecimal into Basic. For example^
if you type F5, the computer will reply:

F5 = PRINT IN BASIC
and then ask for another input. If you type a
non-existent command, say, H2> the computer
replies!

H2 DOES NOT EXIST IN HEX
then ask for another input to be given.

HEX

TO BASIC

16

SCROLL

2©

INPUT m

30

IF R*= n " THEN RUN

46

IF LEN m m 1 THEN GOTO 188

58

LET fi = < 16 * < CODE fi$ <1)
(CODE R$ (2) - 28 >-5

i - 28 > 4

60

SCROLL

70

IF M 255 OR fl< 8 THEN GOTO

100

86

PRINT M$ ; " = " ; CHR$ fi";

"IN BASIC "

96

GOTO 18

188

PRINT fi$ ; " DOES HOT EXIST

IN HEX. "

110

GOTO 18

76 YOUR COMPUTER, JUNE 1382

Over the moon

SOFTWARE FILE.

A Cockbum,

Warrington,

Cheshire.

FOR MY version of the popular Lunar Lander
for a Model A, BBC Micro, first you input
your fiicl allowance and then your flight com-
mences. The lander is dropping out of orbit in
the top left-hand corner of the screen. You
apply upward and horizontal thrust to bring it

to a soft and happy landing on the base pad.

On the right-hand side of the screen you
have your instruments. Alt gives the altitude
in metres; V-V gives the vertical velocity or
descent rate; H-V gives the horizontal velocity
or drift. Fuel gives an indication of how much
fuel is left; bearing indicates horizontal
distance from the landing pad.

From the instruments you can tell exactly
where you are even if you arc off the screen
and it is possible to do blind landings. When
you have used three-quarters of your fuel, a

warning flashes and when all fuel is used the
display flashes red. Assuming you have
successfully landed, the computer then passes
comments on your performance.

As the program is run in Mode 4 it takes up
all but 90 bytes of the user RAM. I have used
multi-statement lines to the full to eliminate
the need for subroutines and to save memory.
Line 10, which is intended to bring the
program back to the beginning when the
escape key is pressed, is best omitted until the
program is running correctly.

_Urtrt LflHSGK

10 OH ERROR RUN

2© flODE 7

39 PRINT TftS <I5> "LUNA WMlfER" " "PRESS U POR UPNftRD THRUST" "PRESS

R FOR REVERSE THRUST" "PRESS 'F' FOR FORWARD TtffcUST"
46 rNRUT-FUEL ftLLOURNCE - , F ' '

56 IF f> 50O f>PINT"SW CflN'T AFFORD THAT MUCH'"" NOWTIHE-TI ME- REPEAT:
UNTIL TIM£*NGWTIHE*206 GOTOlO

60 IF F<100 PRINT-NOT £VEK BUCK ROOERS IS THAT GOOD! "" NQWT I HE-TIME ;
REPEAT UNTIL TIME-HOWTIKE+200 GOTO10
70 PRINT ''"HIT ANV KEV TO STfcftT* -Z-GET
98 MODE 4
S0 MOVE 0,0
tec DRAM 1200,0
II© MOVE 600,4
120 DRAM 600/4

130 F0RO=0 TO 200 PLOT 69,RNIKl,280>,RHDa&2«O NEXT
140 E=0 A=9770:V»e : B*27:K-F:ftL=0
150 PRIHTTRB <35>4.>-ftLT"
loO PRINTTAB <35,$>**V~V
l?0 PRINTTAB <33,12> M H-V"
180 PRINTTAB i33- i6>*FUeL"
150 PRINTTAB <33,20>"BE*RIH&"
2Q% £»E+H ft*ft-y
210 B-[NT<(E-£40>/6.4/

220 ft*A+24 OCOL O, 1 MOVE E-20,A HOVE £+20, A PLOT S5,E,R*20:nOVE
E-20,A-

DRAM E-20,A~16 MOVE E+20,ADRAW E+20/A-16 fl-A-24
230 PRINTTAB <23-5>A
240 PRINTTAB <&,?>VM
250 PRINTTAB <2S, I3>H
260 PRINTTAB <20,17>F
2?0 PRINTTAB C2B*21)B
£80 IF A<0 A-0 GOTO 450
290 0»H-X»V

3S6 IF FC3-F** GOTO 350
SIC C*-lHKEYf <0>
320 IF ttm"F» H*H+i F-F-3
330 IF C*-*R" H*H-1 F*f-3

348 if e#=nr v-v-2;f«f-3

350 *FX 15,0

3€0 IF AL>2 AL«0

370 IF FOC/4 #tW AL<2 PRINTTAB C34,24>"ALft*frP : AL*AL+I IF F-O^VBU

19,1,1,

0,0,0 PRINT TAB <15,15>"N0 FUEL"

3S0 IF AL>1 PRINT TAB <34,24> " =AL+1 1F.F=0VDU 19,1,7,0,0,0

390 If F<K/4 PRINT TAB <35, 28> "FUEL" TAB <33,2?> "WARNING*

400 IF DOH OR I OV: SOUND 0,-10,4,10

410 IF IOV GCOL O.J MOVE E,fi*24I>ftfiH £,ft-3QMOVE £,A*24 = DRAH E-S,ft-30-

MOVE E/A+24DRRW E*8,A-3G:GC0L 0,0 *0vE E.R-3& MOVE E,A+24DRAW

F— 9 R- 30 !

MOVE e7a+24 DRAM E+O,ft-30

420 IF D>H OCOL0, I fi*A+24:M0VE E+20.A DRfiW £+50, ft : MOVE E+20, REDRAW

E+€0,A-4:

MOVE E+20,A'DRAM E+60>A*4 GCOL 0,0MOVE E*20,A DRAW E+60.AMOVE E*20,A-

DRAM E+60,A-4 MOVE E+20,ADRmW E+60. A*4 -- GCOL 0. iA*A-24

438 IF tKH GCOL0,1 A«A*24*H0VE £-20, A DRAW E-60.A MOVE E-20,A-DRAM

E-60-A-4

MOVE E-20.A DRAW E-60 , A+4 : GCOL 0,0 MOVE e-20,ADRAH E-€3,R:rtOVE E-20,A:

DRAW E-«>0,A-4rMOVE E-20,A PR^W E-60, A*4 GCOL 0-1 A*A-24

440 V«V+1

450 NOWTIME-TIME REPEAT UWTILTIME=r^OWTIME+iO

4£0 A-A+24:GC0L 0/0: HOVE E-20,A;MOVE £*20,A PLOT S7,E,A+20MOVE E-20,A

DRAW £-20, A- 16 MOVE E+20,A DPRW E+20,A-lS ff-A-24

470 IF A< 50 GCOL 0* I MOVE 0,0 DRAW 1250*0 MOVE ^00,4 DRAW <SS0,4

4S0 GOTO ISO

490 VDU 30; 19, 1,7,0,0,0

500 IF V<5 AND K-F<300 AMD ABS <BX5- PRINT "HELLO BUCK ROGERS*"

510 IF ABS<B><6 AND VC5 AND <K-F»299 PRINT "GOOD BUT EXTRAVAGENT ! * ■

520 IF V<5 AND H<5 F1?I NT" SMOOTH ! •/*

530 IF V>4 OR H>9 FOR A»0 TO 255 STEP 7 SQU*<DI • -15,A,0NEXT^FORY— 15

TO 0:

SQUND0,Y,4,2.5 NEXT: GCOL o, 1 HQV& E,Q DRAW E-IO0, 180 MOVE E,0 DRAW

E, 100

lO'/E E,0 DRAM E+1G©,100 PR1NT-VOU CRASHED* ! \ m GOTO 570

540 IF V<5 AND H>4 AND HOQ PRINT 'BUMPY' ■

550 IF ABS<8»3: PRINT "BUT VOU ARE -;ABS<B> , "METRES FROM

BASE. - •"WALKi"' '

560 PRINT -VOU USED M ;K-F" FUEL UNITS*"

370 PRINT "MIT SPACE BAR TO CONTINUE" -REPEAT A**GET* UNTILfl*-'

500 GOTO 20

Tunnel vision

D M Jones,

Mold,

C/wyd.

The program prims a random maze and the
player takes the form of the diamond at the top

m^®l

of the screen. The object is to reach the circle
at the bottom of the maze, without colliding
with a wall, in the least number of moves.

On most mazes that the computer forms, it
is impossible to reach the circle without
pressing the nought key. When this key is
pressed the walls immediately above, below, to
the left, and right of your diamond are demol-

ished and disappear. However, using this
feature increases your number of moves by
four.

When you reach the circle you are told your
score and the lowest number of moves the
maze has been completed in so far. The
program itself is fairly basic and sound and
colour could be added for the 3.5K machine.

REM*MflZE*

220 GOTO130

10 PRINr"D"'S-100000

250 M-M+l

20-V»0'M"0

260 P0KEE,32=E»E+G

30 E-INTC 22*RND< 1 )+7?02 )

270 I FPEEK< E )»9 1 THEN350

40 H«INT< 22*RND< 1 H8164 )

280 POKEE/90

50 PR I NT " mm***§MRZ£§****ft*X** "

290 IFE-HTHEN600

60 PRINT" 2 '-DOWN 4<-UP"

300 GOTO 158

70 PRINT" 6 «-LEFT 8= -RIGHT"

530 P0KE36879,27:PRINTW3U HIT R WALL"

75 PRINT" 0: -DEMOLISH"

560 INPUT-RNOTHER GRME<Y/N)"jG*

80 PRINT" ********************** "

570 IFG*""N"THENSTOP

90 FORU-0TO5000'NEXTU*PRINT"D"

580 PRINT"Q"

100 POKE36879.0

590 GOTO20

110 FORfl*lTO230

600 P0KE36879,27<PRINT"WELL DONE! YOU MRDE IT!

tl

120 B*INT<462*RNEXl>+7724>

610 PRINT" IN "M" MOVES."

130 P0KEB,91

620 IFM<STHENS*M

140 NEXTR

630 PRINTTERST MOVES* "8

130 P0KEH,81=GETfl»

640 GOTO560

160 P0KEE.98

1000 IFVOTHENCOTO1020

170 IFP,i="2"THENG«22--GOTO250

1010 GOTO130

188 IFR»«"4"THENG— 22 = G0T0258

1020 P0KEE+1,32=P0KEE-1,32

190 1 Fft*» " 6 " THENG— 1 ' GOTO250

1 030 POKEE+22 , 32 • POKEE-22 , 32 • V» V+ 1 ■ M«M+4

200 I Ffl*» " 8 " THENG- 1 ■ GOTO250

1040 RETURN

210 IFfl*«"0 ,, THENGOSUB1000

■

YOUR COMPUTER, JUNE 1982 77

SHARP

MZ-80K MZ-80A MZ-80B

FUNCTION CASSETTE SOFTWARE

by DALE HUBBARD

BUY 2 at £19.95 - TAKE 1 at £5.95 FREE!!!

All programs in Standard Sharp Basic for 4SK RAM upwards.
All programs supplied with exhaustive and attractively bound documentation.

DATABASE

The program that everyone needs. Facilities include sort, search, list, delete,
change, totals, save file, line print if required, etc., etc. Can be used in
place of any card index application. £19.95

STOCK CONTROL

All the necessary for keeping a control of stock. Routines include stock set
up, user reference no., minimum stock level, financial summary, line print
records, quick stock summary, add stock, delete/change record, and more.

£19.95

HOME ACCOUNTS

Runs a complete home finance package
for you with every facility necessary for
keeping a track of regular and other
expenses, bank account, mortgage, h.p.,
etc., etc., etc.! You'll wonder how you
ever managed without it.

£19.95

MAILING LIST

A superb dedicated database to allow for manipulation of names and
addresses and other data, with selective printing to line printer. Features
include the facility to find a name or detail when only part of that detail is
known. Will print labels in a variety of user specified formats.

£19.95

CHOPIN - LES
ETUDES

Six beautiful studies from Opus
10 and 25, performed by you
live by Mr Sharp -
spellbinding!!

£5.95

INVOICES AND STATEMENTS

Ideal for the small business. A complete suite of programs together with
generated customer file for producing crisp and efficient business invoices and
monthly statements on your line printer. All calculations including VAT
automatic and provision for your own messages on the form produced.

£19.95

THE CATALOGUE

This dedicated database is ideal for use in any situation where a catalogue
could be utilised, e.g. stamp collections, coins, photos, slides, books,
records, etc.

£19.95

MOTOR
ACCOUNTANT

Find out exactly what that car is
costing you and keep a data file
with all your expenses therein!

£5.95

RECIPE FILE

Let all those computer widows have a bash! The
wives will really enjoy the fun of this program
designed to keep all her recipes. Will even
suggest a menu for a day/week! Excellent value.

£19.95

Access welcome. Send cheque, P.O. or cash (registered) or credit card number to:

Gemini Marketing Ltd., Dept. PCW(3>, Quay House, Quay Road, Newton Abbot, Devon TQ12

2BU or telephone us with your credit card order on (0626) 62869.

All orders despatched BY RETURN — no waiting. AH prices include VAT and post and

packing except Hardware. Full range of Sharp peripherals available — please phone for

quotations. Please state machine type (A, K or B) when ordering software.

78 YOUR COMPUTER, JUNE 1982

COMPETITION CORNER

Golden nugget

BY ANTHONY ROBERTS

HERE IS THE PLAN of Old Swan adventure
park. You pay a coin to enter* help yourself to
a nugget in a bag, use it to pay the blind ferry-
man to ferry you to the exit, and leave, You
could pay the ferryman to take you to the
island and pick up a pearl — but it would do
you little good as you then would not be able
to leave the park. However, the Wizard One-
eye has a plan: when you help yourself to a
nugget in its bag substitute a stone for each
nugget before you reach the ferryman who is
too old and blind to notice — provided there is
only one stone per bag of course. If the Wizard
One-eye starts with enough copper coins to
keep on re-entering the park he would finish
up with a fortune, because of the steadily-
increasing number of bags he would be carry-
ing to the island — especially as the stone in
each bag buys its own trip to the island —
except for the final one to reach the exit on
each trip.

The Wizard has arrived with a bag of coins,
and leaves with the maximum number of
nuggets he could obtain — curiously, 32K or
32,768. How many coins did he start with?

PLEASE " » 3
HELP YOURSELF
TO A NUOOET
IN A SAG

WAY HOME

Competition prize winners

THERE were 400 entries for the Memotech
64K RAM pack competition in April. Once
again, most were correct, making the task of
choosing a winner difficult. After some dis-
cussion, the 64K RAM pack was awarded to
N T Fuller of 5 Southbourne Avenue,
Emsworth, Hampshire PO10 8BB, for his "I
need a 64K RAM pack because . . . absence
makes the mi-cro founder".

Other notable entries included M White's
"with 16K, the answer to the ultimate
question comes out 4/2000" and R Whitakcr's
"the monsters in adventure programs need
plenty of byte". B Buck of Northampton was

quick off the mark with "this will open up a
whole new 'spectrum* of programming possib-
ilities" while John Mallon revealed a musical
bent; "she's only 16 but I'll love her even
more at 64".

Stephen Dunning echoed a number of
readers* sentiments with "it drives me up the
wall to see report code four" while Mark
Kirkby waxed lyrical with "I wanna do decent
progin* without the RAM pack wobblin* ".
K Rawkins concluded "then I would be able
to answer the $64,000 question" and Graham
Newcombe decided "IK is K.O.'d, O.K.?".
Last word on the subject went to P Blenkinsop

Solution to
the April
crossword.

who revealed that "playing one-roomed
adventure is becoming a real bore."

The Klingon death competition also drew a
large response. The problem was to find the
deftise button which turned off the automatic
defences which guarded the Klingons'
treasure. Every button, except for the defuse
button, could be pressed in a closed loop
sequence where every button was identical to
the previous button in three of its four
symbols.

One solution was to write a program to look
for the sequence and thus work out the defuse
button. But the easy method was to write a
program which looked for a button which did
not have three symbols which were identical to
two other buttons — because it cannot be part
of a circular loop of buttons. The only button
which fits this description lies in row 4,
column 2 of the control panel:
AM
Aft
The winning solution was sent in by Gcof
Chcyne of Kirkhouse Lodge, Traquair, Inner-
leithen, Peebleshire EH44 6PU. The letters in
his program stand for the following symbols,
A = a black circle, B = a black square, C = a
black triangle and D = a white triangle.

KLINGON BERTH - ZXS1

ig

BIM fi$C€4,4>

15

FOfc X=l TO 64

20

INPUT R*<X>

25

NEXT K

;e0 FOR X*l TO 64

1*5

LET &*-fi*OM TO 3>

11*

LET C*"fl* <X,2 TO >

115

LET D$=tt<X,t)+toiX,$

ro >

126

LET E****<K>i TO £>+ft*<X

125

LET C*0

13tf FOR V-l TO 64

135

IF (VOX fiND BI"fil-AM

TO 3»

OR iVOX AND Cf*Af

TO »

OR (VOX AND B*«RS<V.l

>+ftS<y,3 TO

>>

OR (VOX hHB E*=fi*<V,l

TO 2>+ft*<V,

4»

THEN LET C=C+1

140

NEXT V

145

IF NOT CM THEN PRINT

fi$<X>

■

150

NEXT

YOUR COMPUTER. JUNE 1982 79

ZX81

HARDWARE/ SOFTWARE

NEW! ANALOGUE PORT II

An 8 channel analogue to digital converter, 8 line digital output
and 6 line peripheral select port. Measure up to 8 voltage inputs to
an accuracy of 0.30% (8 bit) enabling the monitoring of almost any
transducer output.

Specifications:

• 100 us convention time

• Full scale sensitivity variable up to 5.0V

•Variable gain amplifier for mV sensitivies on channel
•Stackable connector for printer and RAM pack

• No external power supply needed

• Digital outputs will drive reed relays directly
•3 LED's on board

Assembled and tested £29.95 16 pin DIL header plugs £1

2X81 EXPERIMENTER KIT

(a) 23 + 23 , Edge connector £4

(b) Stacking strip £1.50

(c) Both (a), (b) and veroboard with suggested circuits £7.50
FAST FOURIER TRANSFORM SOFTWARE

For frequency analysis of data; on cassette, with manual £15.20
Please add £1 post and packing to cost of order. Delivery normally
return of post. Money back guarantee if not satisfied. Cheques
and P.O.'s payable to UNIVERSITY COMPUTERS,
Bulk order, official orders accepted.

UNIVERSITY COMPUTERS

5, ST. BARNABAS ROAD,

CAMBRIDGE CB1 2BU

At last 16KZX81

ASTRO-INVADERS

Just look at these features . . s
... then look at the price!

• Superior machine code programming

• Explosive on-screen kill effect

• High-scoring saucers

• Manoeuvring array of 54 attacking aliens

• Photon-torpedoes with rapid fire facility

• Accelerating attack rate

•On-screen kill count with high-score update

• Destructabie defence shields

• Fast action space-graphics

•A new dimension in ZX81 value

Astro-Invaders is yours on cassette with FOUR BONUS GAMES:
ARCADE GRAND PRIX— drive four levels of machine code skill.
PENALTY - get ready for Spain '82; defend your goal against the
sharp-shooting ZX81 .

GOLF — judge shot-strength, angle, bunkers ... and maybe hole
in one!

plus machine code fun with

SWAT — war on the insect world!

5 Amazing games on one cassette for ONLY £3.65 tpost free in
UK). Order yours from:

JOHN PRINCE,

29 Brook Avenue, Levenshulme,

Manchester, M19.

.AMU** 40

QUALITY

VIC-20 GAMES

With full colour and fantastic sound effects

GAMES TAPE 1 (now enhanced) tor the unexpended Vic. 6 great games on one

cassette.

GRAND PRIX: Drive the formula one car along the twisting road avoiding the

boulder. A game not to be missed; very addictive with incredible Hi-Res graphics.

BANDIT: A fabulous version of this famous fruit machine game. You may have l0*t

in the past but this one's a winner. You won't be disappointed.

APOLLO DISASTER: Fast shooting and a cool head are needed for this outstanding

qame (min-dbtowing graphics).

RED ALERT: Can you save the earth in the face of the ev3 chemical "Vicoric Acid"?

RIFLE RANGE: At home on the range you am faced with the big shoot out. An

exerting game for two players.

ACEY DUCEY: Can you outwit the computer in this great card game. Great all round

effects.

EDUCATIONAL PACKI! for the Vic * 3K expansion

LUNAR MATHS: A must for youngsters up to the age of 7. To get the ApoKo space

craft to the moon and back you must answer 10 selected maths questions.

Big bold graphics, simple touch key entry make this an easy game for any
youngster to use.

3K RAM PACKS ARE AVAILABLE ON REQUEST AT £29.35 + £1.05 P8P

ADVERTISING PACKS (dealers only)

Shop window advertising /demonstration programs undertaken on request. We

already have a large stock (standard} waiting for your order. Phone for more details.

Can you write Basic/Machine Code games and educational programs for the Vic. If
so send them on cassette to the address below, or give us a ring. 15% royalty or a
lump sum paid on all accepted programs.

Basic consultancy. If you have a business with problems or need advice on computer
matters phone Titan Programs now!

Games Tape 1 €5 {fully inclusive*

Lunar Maths £6 (fully inclusive!

3K RAM packs (required for Lunar Maths only) £29.95 + £1.05 p&p

for instant despatch send cheque or PO to:

TITAN PROGRAMS

83 Ashwood Road, Rudloe, Corsham, Wiltshire SN13 0LG
Telephone: Chippenham (0249) 55854, Hawthorn (0225) 810132

ZX81

owners

have you seen
A book of

30 PROGRAMS

For Only £4.95
NO MEMORY EXPANSION NEEDED

Each program has been designed to fit into 1K of RAM

TEACH YOURSELF PROGRAMMING

Comprehensive explanations of each listing will teach
you many techniques of ZX81 programming.

HOURS OF AMUSEMENT

With titles such as FORTRESS, BALLOON, and ODD MAN
OUT, you could easily become a ZX81 addict. Pius,
entirely new implementations of well-known favourites;
LUNAR LANDING, MASTER CODE, ORBITAL INVADERS,
and many others.

CASSETTE AVAILABLE TOO!

If you order the book you can also buy the

programs on a quality cassette for only

£4.95 extra.

Please send me:

copies of the book at
£4.95 each

copies of the book and
cassette at £9.90 pair

Please send your orders
with cheques/PO's to:
Richard Francis, Dept-YC A/ S
22 Foxhollow, BarhilL
Cambridge, CB3 8EP.

80 YOUR COMPUTER, JUNE 1982

12 PROGRAMS £3.50

9 for Ik plus 3 expanded for 16k ;

Including:

* BIORYTHMS PLOTTER

* MOON LANDING GAME

* TELEPHONE CHARGES

* ESP TESTER

* LOANS & MORTGAGES

Games and Household Management programs written
in BASIC and machine code. Recorded both sides.
Please allow 10-14 days for delivery.

I f/tictomaaia YC 6 j

^1/2 Wilson St., Bristol BS2 9HH.

Please send me cassettes at £3-50

I enclose a cheque/postal order for £

Name; . ■ ■ i j ■ i i i i i__i i i i — i — i — i

Address

i i i i_

I I I u

-I L

_l I I I 1 I l_

r

ZX 81 64K
RAM EXPANSION PACK

• ■ •
v .:'/..:;<•■/. ■■■■!•:.' • -,' -. -

>/

J L

jL_r i l

J I I

Quite simply good value for money at £58.65 including VAT plus

£1.50 P&P. Contained in a specially designed plastic case.

ZX81 16K RAM EXPANSION PACK also available as above

£32inc VAT + £1.50 p&p.

Junior Maths Pack One to run on 1K RAM 2X81 — five helpful

programmes on cassette for £3.75 inclusive. Logic, Sums,

Nimb, Division & Money.

12 MONTHS GUARANTEE. DELIVERY 14 DAYS

*See our April issue advertisement for Vic 20 Product details*

CEL CUSTOMISED ELECTRONICS LIMITED

Winker Green Mills, Stanningley Road, Armley,

Leeds LS12 3BB. Telephone 0532 792332

155 Marton Road, Middlesbrough, Cleveland TS4 2EN.

Telephone 0642 247727

m

NEW ZX81

16K SOFTWARE

THE DIGGLES KITCHEN
RECIPE CASSETTES

CELEBRATION DINNERS TO
SIMPLE SUPPERS

VOLUME 1

pages of world

3 recipes
VAT)

VOLUME 2

50 pages of European recipes
£4.99 (inc. p&p and VAT)

SPECIAL OFFER - both volumes for only £9.00

inc. p&p and VAT

More volumes to follow

Mail Order Only — please specify which volume(s)

Send remittance to:

MICRO COMPUTER SOFTWARE

Unit D6, Pear Industrial Estate,

Stockport Road, Lower Bredbury,

Stockport SK6 2BP Tel: 061-494 2441

COMPUTER

is your magazine — every issue
is full of articles specially written for the
home computer enthusiast.

Reviews of personal computers;
Programs: Surveys of software available on
the market: New application ideas for your
computer; Computer Club — news from your clubs;
Calculator page: Letters; Answers to your problems
and pages and pages of computer games and
program listings.

All for only 60p
Ensure your copy
each month, take
out a subscription
NOW!

SEE THE

SUBSCRIPTION

ORDER FORM BETWEEN

PAGES 90 & 91

IN THIS ISSUE

YOUR COMPUTER, JUNE 1982 81

THE ZX81
COMPANION

ISBN 90721 01 1
Price £7.95 incl. UK P&P

If you have a Sinclair ZX81 and want to use it to its full
potential then, as the experts have all agreed, this is the book
for you. It contains detailed guidelines and documented
programs in the areas of gaming, information retrieval and
education, as well as a unique listing of the 8K ROM for
machine code applications.

'Far and away the best . . . once again Linsac has produced the
book for the serious end of the market'. — Your Computer,
November 198L

'The ZX81 Companion is a most professional product . .
many good illustrative programs, tips and warnings'. —
Education Equipment, October 198h

with

'Bob Maunder's attempt to show meaningful uses of the
machine is brilliantly successful . . . thoughtfully written,
detailed and illustrated with meaningful programs ... To
conclude — the book is definitely an outstandingly useful
second step for the ZX81 user'. — Educational ZX80f 87 Users'
Group Newsletter, September t98h

Send you cheque for £7.95 to:

LINSAC

68 Barker Road, Linthorpe
(YC) Middlesbrough TS5 5ES

WELCOME,
SPECTRUM!

RD Laboratories are pleased to continue supplying
Realtime Interface Modules for economic micro
control and instrumentation — suitable for all ZX
Computers* Including Clive Sinclair's brilliant new
ZX Spectrum!

The RD 8100 Modules can be used in many
applications: —

• DATA LOGGING

• CONTROL

• AUTOMATIC TESTING

• INTERACTIVE GRAPHICS

• GAMES AND LEISURE ACTIVITY

The RD 8100 Module range consists of Logic
Input/Output Port; Analogue Input Port; Analogue
Multiplexer/Amplifier; Analogue Output Port; Light
Pen Module,

For full details of the RD 8100 System, please send
a stamp and your address to Department CY at RD
Laboratories.

&>

R D Laboratories

S Kennedy Road, Dane End, Ware, Horts. SG1S OLU

(09201 84380

zyr***

H<?//

ELECTRIC

PErOL

campflnv

PRESENTS

SH ASTERDIOS

AUTHOR Robert J Wray
(c)EPC I982

-FEATURES-

1 IOO% Machine code 5k,

2 Carefully designed graphics

3 Full screen ship control

4 *Smart* hunter-killer UFO

5 5 speeds 5 high scores

6 On screen scoring & status

7 1 or 2 players

B Nlulti fire laser cannon
9 Speed increases during game
10 Money back guarantee

£4.95

EPC 1 MOUNTVERNON BILTON N- Humberside
All Trade equiries welcome

WHAT CAN I DO WITH 1K?

If your answer is not much, then you must read
Roger Valentine's book "What Can i Do With IK?
(40 programs and routines for the 1K Sinclair ZX8D".

". . . a splendid book and one which will repay your
investment time and time again." (ZX Computing).

Book £4.95.

Also available on cassette £4.95.

NENN

WHAT CAN I DO WITH 16K?

The companion volume to the above, containing
complete program listings for 16K.

Book £4.95.

Cassettes available individually — ask for list,

ZX81

Probably the best ZX program ever written for the

serious business user.

Cassette £10.00. Full maintenance contract available.

V & H Computer Services

182c Kingston Road

Staines

Middlesex

Tel: Staines 58041

L0 p*j***«* * «*'■-<*

*u **i IK * «.*« 2*11

82 YOUR COMPUTER, JUNE 1982

Wida Software

Specialists in Educational Software For Schoois and Colleges

WORDPACK

NEW ZX81 NEW

EDUCATIONAL SOFTWARE

AUTHORING PROGRAMS

FOR TEACHERS AND STUDENTS

•Write and Solve your own tests
•Write and Play your own word games
•Write and Solve your own puzzles

Wordpack 1
Wordpack 2 £450

Wordpack 3
Wordpack 4 wlf!

Ail for 7X81 with 16K
* payment by cheque or credit card

Send s.a.e. for catalogue of educational software for Apple If,

PET, ZX8f

AJ prices incl VAT:

vra

WIDA SOFTWARE 2 N*c*K>ias Gardens. London W5 SHY. Tel: 01-567 6$41

MASTERMIND
CHALLENGER

ZX81 16K

• Competes against you to find your secret
number before you deduce its secret number.

• Operates on 5 digit numbers,

• Handles any number of repeats of one or more
digits.

• Pvlaintains a record of all tries and scores during
a game.

• Validity checks on entries.
Supplied on cassette £4.95 inc. p&p

Cottage Software
2 Tilmans Mead
Farningham, Kent DA4 OBY

xxxxxxxxxxxxxxxxx AlUN %& mMM&%0

* First £50 PrizeT *

©dMSHPETTOWIKI

PLUS 10 RUNNER UP PRIZES

By following the clues and overcoming the obstacles
can you solve the mystery of the "DEATH SATELLITE"
and unlock its secrets???

Your ATOM will require 12KRAM. <F Point NOT Requred)

Full competition deioHs suppled with all orders

PRICE « . 6.00

USERS

OTHER ATOM TITLES

POLECAT *_4.95 EARLY WARNING :_£.95

MINEFIELD t*_4 . 95 ROBOT NIM -_3 . 95

ATOMIC CUBE__uu4.95 POLARIS *_3.95

_3.95

CYLON ATTACK

In this 3D all action game, hi-resolution graphics
are used to simulate the pilots view of space
from the cockpit of his Starfighier.
Your instruments are constantly displayed and
include -Long range scanner - Laser energy status-
and fuel status. Score and Hi -score also displayed

Written in m/c for the ATOM using 5K text 6K graphic

PRICE. CS5

WE PAY 25% ROYALTIES ON YOUR PROGRAMS
ORDERS TO A&F SOFTWARE 10.WILPSHIRE AVE, LCNGSIGHT,

MISSILE CGMMAND_j^4.95 PONTOON

• ■ 5Ktexl SKgraphics •♦ * 5K text V2graphics
x = Floating Point Required

cftfea &7&&V& *»V£ &V& &** £»V»«tfrt d*Vs>
MVNW WttlMWt HWff W? HWd W?

ATOM SUPERCOS

Tired of waiting for your programs to load?
SUPERCOS is a low cost HIGH SPEED 0200 bctjd) COS

rj witt be able to save/toad 5 times faster than normal.
addition SUPERCOS provides visible load, program test
verifying, plus 8 other commands. Rec's 1-25 RAM only 5*95

©OB© RJMKM

Two popular games from our Atom range converted and
enhanced to run on BOTH MODEL A&B MICRO'S

EARLY WARNING Destroy the attacking waves of ICBMs
using a radar tracking system and intercept missies.
48 Levels -Each one harder than the last $.00

POLECAT Find your way through the warren onto the
surface and return to your burrow with winter supples
Easy!!! BEWARE THE POLECATS 6,00

SPECIAL OFFER Deduct 1.00 per additional cassette when you
-order 2 or more programs

MANCHESTER, M12 STL [Access/Bc-ctay card on {060 320 5^82]

YOUR COMPUTER, JUNE 1382 83

ZX80/1
WAR!

Price

ZX KEYBOARD
FULLY CASED
wuh REPEAT KEY

Fully CASED KEYBOARD £37.95
Uncased KEYBOARD £27.95

KEYBOARD CASE £10.95

This is a highly professional keyboard using executive
buttons as found on top quality computers. It has a repeat
key and comes complete in its own luxury case. This is a
genuine professional keyboard and should not be confused
with toy keyboards currently available on the market.

16K RAMPACKS

MASSIVE ADD ON MEMORY

WHY WAIT TO PAY MORE
FAST IMMEDIATE DELIVERY

**k

Post to

Dept. YC2

KAYDE Electronic Systems

48/49 Exmouth Road

Great Yarmouth

Norfolk NR30 3DP

Tel: (0493) 57867

All products include VAT and are fully
built and tested and come with a complete
money back guarantee.

Please send me RAM Packs £32.95 each

Please send me Cased Keyboards £37.95 each

Please send me ....Uncased Keyboard £27.95 each
Please send me Keyboard Case £10.95 each

I enclose £

Name....

Address.

Please add £1.50 p&p and make cheques payable to
Kayde Electronic Systems.

84 YOUR COMPUTER. JUNE 1982

THE NEW &

EXCITING

TRS80

MODEL

III

48K
£599

• VAT

The Radto Shack TRS 80™ Model til ts a ROM-based
computer system consisting of:

• A 12 inch screen to display results and other information

• A 65 key console keyboard for tr^utting programs and data
to the Compute? • A 2 80 Microprocessor, the "brains of
the system *A Realtime Clock •Read Only Memory
(ROM) containing the Model IM BASIC Language (fully
compatible with most Model I 8A$IC programs) •Random
Access Memory (RAM) for storage of programs and data
whtle the Computer is on (amount is expandable from ** 16K"
to "48K". optional extra) • A Cassette Interface for lonfl term
storage of programs and d3ta (requires a separate cassette
recorder, optional extra) • A Printer Interface for h$rd*eopy
output of pfocjrams and data {requires a separate line printer,
optional extra) •Expansion area to-' upgrading to a disk
based system (optional extra) * Expansion area for an R$*
232-C serial communications interface (Oplk>nal extra)
All these components are contained in a single molded case,
and an are powered via one power cord.

0»sc Drives Kit with 2x40 Track Drives - £59Q + VAT
Disc Drives Kit with 2x80 Track Drives - £729 * VAT

HITACHI

PROFESSIONAL

MONITORS

' - £A2$ £99.95
12"-£WSF£149

h

• Reliability Solid state orcuitry using an IC and silicon
transistors ensures hvgh reliability- • 500 lln#t horizontal
resolution Horizontal resolution m excess of 500 lines is
achieved in picture center, • Stable picture Even played
back pictures of VTR can be displayed without jittering.

• Looping video input Video input can be looped through
with built-in termination switch. • External syne opera-
tion (available as option for U and C types) • Compact
construction Two monitors are mountabte S»de by side m a

standard 19 inch rack.

ACORN ATOM

UNIQUE IN CONCEPT -
THE HOME COMPUTER
THAT GROWS AS YOU DO

Fully Assembled £157.50 * VA"

inc. PSU

Special features include • Full Sued Keyboard •
Assembler and 83S»c *Top Quality Moulded Case
Optional High Resolution Colour Graphics *ooX)2
Microprocessor

THE EPSON MX SERIES

*^>«j^Ti*

i • $0/132 Column

i^JSSSvSS^**^

* • Centronics Parallel

• Bi-directional

' :\*tt^£\

• Upper & lower case

• True Descenders

J^T^^'t

• 9x9 Dot Matrix

w^^^&wm

• Condensed and

—^

Enlarged Characters

• Interfaces ar*6

Ribbons available

MX80T

£339 - vat

MX80F/T

£389 vat

f

MICROLINE 80

£289 < vat

• 30 CD* Un. directional • Small size: 342 iW) * 254 (D) *
108 (HI mm. • 160 Characters. 9S ASCII and 64 graphics »3
Character sizes: 40, 80 or 132 chars /line • Faction
and P*n Feed •Low noise: 65 dB • Low weight: 6.5 kg

Ideal for smaV businesses, schools, coHeges, homes, etc
Suitable for the experienced, inexperienced, hobbyist,
teacher, etc

rOMPUKIT UK101

6502 based system - best value tor money on the
market * Powerful 8K Basic Fastest around * Ft/:
Qwerty Keyboard * IK RAM Expandable to SK on board.
* Power supply and RF Modulator on board. *No Extras
needed — Plug-'n and go * Kansas City Tape Interface on

board. *Free Sampler Tape including powerful
Disassembler and Monitor with each Kit * If you want to
Itarn about Micros, but dtdn't know which machine
to buy then fhi< .v me machine for you

KIT ONLY £99.95- . VAT \ *■*£*%»

Fully Assembled - £149 - vat J Packing

WE ARE NOW STOCKING THE
APPLE II AT REDUCED PRICES

AUTOSTART
EURQPLUS
48K
£649

- VAT

Getting Started APPLE II *s faster, smaller, and more
powerful than its predecessors. And it's more fun to use too
because of butlt >n features like:

• BASIC The Language that Makes Programming Pvn.

• H?g/h Resolution Graphics tin a 54,000 Point Array* for
Pi nary- Detailed Displays • Sound Capability that Brings
Programs to Life • Hand Controls for Games and Other
Human-Input Applications, •internal Memory Capacity of
48K Bytes of RAM, 12K Bytes of ROM; for Big System Per
forma nee m a Small Package, •Eight Accessory Expansion
Sk>ts to let the System Grow With Your Needs.

You don't need to be an expert to enjoy APPLE it it >s a
complete, ready-to run computer. Just connect it to a video
display and start using programs tor writing your own) the
f rst day. You'll find that its tutorial manuals help you make it
your own personal proOIem solver

NOW INCLUDED: Sound, Upper and lower case. Extended
BASIC a.nc Machine Code enabling the Writing and
Execution of Machine Codes Programming direct from
Keyboard .

1SK RAM. 12K Mcrosoft BASIC
Extensive Software Range.

Self- Contained PSU UHF Modulator Cassette. External
Cassette Interface. Simply plugs into TV or Monitor
Complete and Ready to Go. Display is 6 lines by 32 or 64
Characters Swuchabtc. 3 Mannuais included. Users Guide,
Beginners Programming and BASIC Reference MannudL
BASIC Program Tape Supplied. Pixel Graphics.

£299 vat

The NEW GENIE II an ideal Business Machine 13K
Microsoft BASIC »n ROM. 7\ Keyboard. Numeric Keypad.
Upper & Lower Case. Standard Flashing Cursor. Cassette
Interface T6K RAM Expanded externally to 40K

GENIE I & 1 1 EXPANSION UNIT
WITH 32K RAM £199 vat

PARALLEL PRINTER INTERFACE CARD
£35.00 -VAT

TEAC

DISK

DRIVES

• TEAC FD-50A has 40 tracks giving 125K Bytes
unformatted single density capacity.

• The FD-50A can be used in double density recording
mode.

• The FD 50A is Shugart SA400 interface compatible.

• Directry compatible with Tandy TRS80 expansion
interface.

• Also interfaces with Video Genie, SWTP, TR$80,
North Star Norton, Supe* brain, Nascom, etc, etc

• Address selection for Daisy chaining up to 4 Disks.

• Disks plus power supply housed in an attractive grey
case.

40 TRACK
Single TOW

Disk Drive ■ ■ ■ M

VAT

Double
Disk Drive

£389 -VAT

77 TRACK
Single P9QQ
Disk Drive L ^* K '

VAT

Double

Disfc Drivt*

£499 -vat

or phone your order

Delivery is added at cost. Please make cheques and postal orders payable to COMPSHOP LTD.
quoting BARCLAYCARD, ACCESS, DINERS CLUB or AMERICAN EXPRESS number

l/, F J l g« ] ;l>lJ; T JiM»ra !TiT2^^W CREDIT FACILITIES ARRANGED send S.A.E. for application form

14 Station Road, New Bamet, Hertfordshire, EN5 1QW CCtose to New 8arnex 8R Station - Moorgaw Line).
Telephone: 01-441 2922 (Sales* 01-449 6596 Telex: 298755 TELCOM G
OPEN (BARNET) — 10am - 7pm - Monday to Saturday

"Europes Largest Discount
Personal Computer Stores"

NEW WEST END SHOWROOM:

311 Edgware Road, London W2. Telephone: 01-262 0387
OPEN (LONDON) - 10am - 6pm — Monday to Saturday

jk IRELAND: T9 Herbert Street. Oublin 2. Telephone Dublin 604165

TELEPHONE SALES

OPEN 24 hrs. 7 days a week

01-449 6596

YOUR COMPUTER, JUNE 1982 85

JRS SOFTWARE

19 WAYSIDE AVENUE, WORTHING, SUSSEX, BN13 3JU
TELEPHONE WORTHING 66691 (Evenings and Weekends only)

CASSETTE prut*»s$i0r>au v receded bv
SOUND NEWS SfuDlOS

GAMES PACK - fleer Ous for ***#»/ 5 x f$K p/pgrems PLUS 2 * IK ptyprmms

3-D Battle {M/code 1K) — Fast moving space battle with continuous count down I

of cne'uv units left
City Bomb (M/code*1K) - Destroy the bu*ldmy$ and lane* your plane You* tue)

has nearly gone jnd you circle the city lower and rower

Warp Were (Basic & M/eod* 16K) - ^natures realistic space craft moved by M code for
(previously sold at Microfa»r with instant response
Sweet Tooth for f4 95*

Snake < Basic -16K) - A garnet of thought and skill Pass through all the ^diked

{previously sold at M»crofair squares without crossing or doubling back on your path
for f3 95' but watch out tor the expanding black blob

Sweet Tooth (Basic ft M/cod© 16K) — M code routines used to move your fat lace round the

screen and gobble the sweets

PLUS Slalom and Black Holes (previously sold together for »4 96:

TOOLKIT

An ESSENTIAL addition to your IK RAM 7X81 (or 2X80 8K ROM)

't*w*.(***> sMt** aimIi when f»r<lt*inigi
(written by PAUL HOLMES)

Provides the following additional tin ihtws

Line renumber you state starting number and increment value

Search and replace changes every occurence of a character as you require

Free space tens you how many free bytes you have left

SPECIAL GRAPHICS ROUTINES

Hyper graphics mode graphics never seen on a ZX81 before

Open instantly sets up as many empty print lines as yqu require »IK version only'

Fill used m conjunction with OPEN fills your screen instantly with your

specified character

Reverse changes each character on your screen to its inverse video

TAPE ROUTINE provides a system WAIT condition unttt a *igna« is received in
the cassette ear jack many uses ■

All these routines are written m machine code and together rake up only
1r><* BYTES Of your precious RAM an incredible achievement n

The price i* incredible too' ONLY £3.96 ($7.90) for cassette, including FULL

instructions arx<S example programs.

ALSO available 16K version ONLY £4.95 ($9.90) which includes all the above PLUS

GOTO's and GOSUB's included m hne renumber

Search for and list every line containing specified character

10K VERSION

As reviewed in 'YOUR COMPUTER'
March 1982

16K RAM PACK
£35 ($69.95)

WHY PAY
MORE

Fuliy built, tested and guaranteed.
No additional power supply required,
black case

No wobble problems - fully
compatible with printer etc, etc
(Please send large S.A.E. + 50p for a
copy of YOUR COMPUTER' RAM
pack reviews (March 1982) —
Refunded when you- purchase the
RAM pack). Please allow 21 days for
delivery

STOP PRESS

NOW AVAILABLE - 64K RAM pack
I56K useable) £75 inclusive

GRAPHICS TOOLKIT

(Another masterpiece by PAUL HOLMES)
22 exciting MACHINE CODE routines that give you control over your screen as never before !

(ZX81 - 16K RAM ONLY)

DRAW/UNDRAW draws or deletes your SCROLL facilities

multi character shape which is defined in a REM UPSCROLL

statement. You may define as many different
shapes as you like and draw or undraw each at
will at whichever screen position you choose

FOREGROUND ON/OFF use this to protect*
existing characters on your screen, When on new
shapes will appear to slide behind and re-emerge
from other shapes

BORDER/UNBORDER Draws a border round the
edges of your screen area. Edit lines can be used
if required. Your border is protected when
foreground is on

FILL Fills any number of lines you specify, starting
at any line you specify, by your chosen character

REVERSE Converts all characters to their inverse
video, control as in FILL

}

Scroll your screen in the
direction indicated

PRINT POSITION CONTROLS
UP

your next PRINT position in
Jirection indicated

prin t PUsniUN ui
UP 1

DOWN L After i
LEPT the dir

RIGHT J

EDITPRINT Moves next PRINT position to first
edit line

ALL FOR ONLY £5.95 ($11.90)

(amazing value from JRS)

DOWNSCROLL
RIGHTSCROLL
LEFTSCROLL

ONSCREEN/OFFSCREEN turns your screen on or
off

BACKGROUND ON/OFF
Fills your screen by your specified character.
When foreground is on existing information is
unaffected and shapes will appear to pass in front
of your background, without deleting it

SEARCH AND REPLACE will search the screen fcr
every occurence of the character you specify and
replace it with your new character

SQUARE draws a square or rectangle from your
specified co-ordinates

ALL these routines are in machine code for
SUPER-FAST response \ Simply load GRAPHICS
TOOLKIT, which repositions itself at the end of
your RAM, and then your own program (or key in
a new one), GRAPHICS TOOLKIT uses only 2K of
your RAM and that includes space to load the
programmers TOOLKIT described above (16K
RAM version)

This includes a cassette with 2 copies of the program
plus a comprehensive instruction booklet with
examples

NOTE: All prices are fully inclusive - send cheque or P.O. to JRS Software at above address

OVERSEAS CUSTOMERS Payment may be made in Sterling {Money Order available at
PLEASE NOTE your bank) ou $U.S. (U.S.A. customers only).

Prices quoted above are also export
prices and include AIRMAIL postage

86 YOUR COMPUTER, JUNE 1982

When you outgrow your personal computer
that's the time you'll wish you'd bought a DAI.

Very low priced personal computers can leave you

feeling very low, after the initial novelty has worn off.

Having learned what the computer can do, you then

find out what it can't do. Unless you expand the system.

And that can set you back a few hundred pounds for

items such as extra RAM and serial interface. In fact,

more than you paid in the first place!

So when you've done all the sums, you'll realise that

the DAI personal computer offers incredibly good value

for money.

Just look what you get for the all-in price.

48K RAM.

24K ROM-based software that
includes a fast BASIC interpreter,
scrolling screen editor, machine
code utility program, twin cassette
tile handling, and disc support.
A full duplex RS232 serial interface
allowing direct connection of a
printer (with resident software
support) and other peripherals,
A parallel interface for connection
of the CP/M compatible DAI disc
unit and other user devices.
Superb 16-colour high resolution
graphics (256x336).

DAI

6. Sound commands for music
generation.

7. Standard TV interface via aerial
socket.

These standard features pave the way for a whole new
vista of personal computing possibilities.
Find out more by completing the coupon today.
Large range of "Dainasoft" software available, e.g.
viewdata, word processing, educational, games . . ,

m?.

DAI

Data Applications
[Uh] Ltd.

a DAI sets you up for life 16B DYER STREET. CIRENCESTER.

GLOUCESTERSHIRE GL7 2PF
TELEPHONE:

CIRENCESTER (0285) 61828 or 2588
TELEX: 43605 BECHAM G

I

•^

5^\

i f v;;;v.

Please send me further details about the DAI Personal Computer.
My interest areas are

Pfeose send me a list of dealers
NAME: .

ADDRESS:

TEL. NO.:

Send to DAI. T68 Dyer Street. Cirencester, Glos. GL7 2PF

Sinclair ZX81 Personal Com
the heart of a system
that grows with you.

1980 saw a genuine breakthrough -
the Sinclair ZX80, world's first com-
plete personal computer for under
£100. Not surprisingly, over 50,000
were sold.

In March 1981, the Sinclair lead
increased dramatically. Forjust
£69.95 the Sinclair ZX81 offers even
more advanced facilities at an even
lower price. Initially, even we were
surprised by the demand - over
50,000 in the first 3 months!

Today, the Si nclairZX81 is the
heart of a computer system. You can
add 16-times more memory with the
ZX RAM pack. The ZX Printer offers
an unbeatable combination of
performance and price. And the ZX
Software library is growing every day.

Lower price: higher capability

With the ZX81, it's still very simple to
teach yourself computing, but the
ZX81 packs even greater working
capability than the ZX80.

It uses the same micro-processor,
but incorporates a new, more power-
ful 8K BASIC ROM - the 'trained
intelligence' of the computer. This
chip works in decimals, handles logs
and trig, allows you to plot graphs,
and builds up animated displays.

And the ZX81 incorporates other
operation refinements - the facility
to load and save named programs
on cassette, for example, and to
drive the new ZX Printer.

Every ZXS1 comes with a comprehensive, specially- written
manual - a complete course in BASIC programming, from
first principles to complex programs.

Higher specification, lower price -
how's it done?

Quite simply, by design. The ZX80
reduced the chips in a working
computer from 40 or so, to 21. The
ZX81 reduces the 21 to 4!

The secret lies in a totally new
master chip. Designed by Sinclair
and custom-built in Britain, this
unique chip replaces 18 chips from
theZX80!

New, improved specification

• Z80A micro-processor - new
faster version of the famous Z80
chip, widely recognised as the best
ever made.

• Unique 'one-touch' keyword
entry: the ZX81 eliminates a great
deal of tiresome typing. Key words
(RUN, LIST, PRINT, etc.) have their
own single-key entry.

• Unique syntax-check and report
codes identify programming errors
immediately.

• Full range of mathematical and
scientific functions accurate to eight
decimal places.

• Graph-drawing and animated-
display facilities.

• Multi-dimensional string and
numerical arrays.

• Up to 26 FOR/NEXT loops.

• Randomise function - useful for
games as well as serious applications.

• Cassette LOAD and SAVE with
named programs.

• 1K-byte RAM expandable to 16K
bytes with Sinclair RAM pack.

• Able to drive the new Sinclair
printer.

• Advanced 4-chip design: micro-
processor, ROM, RAM, plus master
chip - unique, custom-built chip
replacing 18 ZX80 chips.

Built:

Kit or built - it's up to you!

You'll be surprised how easy the
ZX81 kit is to build: just four chips to
assemble (plus, of course the other
discrete components) - a few hours'
work with a fine-tipped soldering iron.
And you may already have a suitable
mains adaptor - 700 mA at 9 V DC
nominal unregulated (supplied with
built version).

Kit and built versions come com-
plete with all leads to connect to
your TV (colour or black and white)
and cassette recorder.

iter-

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16K byte RAM

pack for massive
add-on memory.

Designed as a complete module to
fit your Sinclair ZX80 or ZX81, the
RAM pack simply plugs into the
existing expansion port at the rear
of the computer to multiply your
data/program storage by 16!

Use it for long and complex
programs or as a personal database.
Yet it costs as little as half the price
of competitive additional memory.

With the RAM pack, you can
also run some of the more sophisti-
cated ZX Software - the Business &
Household management systems
for example.

inczlalr"

ZX8I

6 Kings Parade, Cambridge, Cambs., CB2 1SN.
Tel: (0276) 66104 & 21282.

Available now-
the ZX Printer
for only £59.*

Designed exclusively for use with
theZX81 (and ZX80 with 8K BASIC
ROM), the printer offers full alpha-
numerics and highly sophisticated
graphics.

A special feature is COPY, which
prints out exactly what is on the
whole TV screen without the need
for further intructions.

At last you can have a hard copy
of your program listings -particularly
useful when writing or editing
programs.

And of course you can print out
your results for permanent records
or sending to a friend.

Printing speed is 50 characters
per second, with 32 characters per
line and 9 lines per vertical inch.

The ZX Printer connects to the rear
of your computer - using a stackable
connector so you can plug in a RAM
pack as well. A roll of paper (65 ft
long x 4 in wide) is supplied, along
with full instructions.

How to order your ZX81

BY PHONE - Access, Barclaycard or
Trustcard holders can call
01-200 0200 for personal attention
24 hours a day, every day.
BY FREEPOST - use the no-stamp-
needed coupon below. You can pay

by cheque, postal order, Access,
Barclaycard or Trustcard.
EITHER WAY -please allow up to
28 days for delivery. And there's a
14-day money-back option. We want
you to be satisfied beyond doubt -
and we have no doubt that you will be.

i

To: Sinclair Research, FREEPOST, Cambertey, Surrey, GU15 3BR.

Qty Item Cade

Sinclair ZX81 Personal Computer kit(s). Price includes
ZX81 BASIC manual, excludes mains adaptor.

12

Item price
£

49.95

Ready-assembled Sinclair 2X81 Personal Computer(s).
Price includes ZX81 BASIC manual and mams adaptor.

Mains Adaptors) (700 rnA at 9 V DC nominal unregulated).

16K-BYTE RAM pack.

Sinclair ZX Printer

8K BASIC ROM to fitZX80.

Post and Packing,

11

$9.95

10

18

27

17

8.95^
29.95
59.95
19.95

Order

Total
£

2.95

D Please tick if you require a VAT receipt TOTAL £

*l enclose a cheque/postal order payable to Sinclair Research Ltd, for £

*Please charge to my Access/Barclaycard/Trustcard account no.

•Please delete/complete as applicable. I I I I I I I I I I I I | —

i i i i

Please print.

Name: Mr/Mrs/Miss
Address: I I LJL

I I > I I • I I I I I I I I I

I ah^-I I I I I I I I I I I I I I I I I I I I I I I I

I :: I I I I I I I I I I I I I I I I I I I I I I I I I

FREEPOST - no stamp needed. yoc os

Make the most of your
Sinclair ZX Computer...

Sinclair ZX

software
on cassette.

E3«— per cassette.

The unprecedented popularity of
the ZX Scries of Sinclair Personal
Computers has generated a large
volume of programs written by users.

Sinclair has undertaken to
publish the most elegant of these
on pre-recorded cassettes. Each
program is carefully vetted for
interest and quality* and then
grouped with other programs to
form a single-subject cassette.

Each cassette costs £3.95
(including VAT and p&p) and comes
complete with fall instructions.

Although primarily designed
for the Sinclair ZX81 ? many of the
cassettes are suitable for running
on a Sinclair ZX8Q- if fitted with a
replacement 8K BASIC ROM.

Some of the more elaborate
programs can be run only on a
Sinclair ZX Personal Computer
augmented bv a 16K-bvte add-on
RAM pack.

This RAM pack is described
below. And the description of each
cassette makes it clear what
hardware is required.

16K-BYTE RAM pack

The 16K-byte RAM pack provides
16-timcs more memory in one
complete module. Compatible with
theZX81WtheZX80>itcanbcu$cd
for program storage or as a database.

The RAM pack simply plugs
into the existing expansion port on
the rear of a Sinclair ZX Personal
Computer.

Cassette 1 -Games

For ZX8I (and ZX80 with 8K
BASIC ROM)

ORBIT -your space craft's
mission is to pick up a very valuable
cargo that's in orbit around a star.

SNIPER -you're surrounded
by 40 of the enemy. How quickly
can you spot and shoot them when
they appear?

METEORS -your starship is
cruising through space when you
meet a meteor storm. How long can
you dodge the deadly danger?

LIFE -J. H. Conway's 'Game of
Life' has achieved tremendous
popularity in the computing world.
Study the life, death and evolution
patterns of cells.

WOLFPACK-your naval
destroyer is on a submarine hunt.
The depth charges are armed, but
must be fired with precision,

GOLF- what's your handicap?
It's a tricky course but you control
the strength of your shots.

Cassette 2 -Junior

ForZX81 with I6K RAM pack

CRASH -simple addition -with
the added attraction of a car crash
if you get it wrong.

MULTIPLY-Iong multi-
plication with five levels of
difficulty. If the answers wrong -
the solution is explained.

TRAIN- multiplication tests
against the computer The winner's
train reaches the station first

FRACTIONS - fractions
explained at three levels of
difficulty. A tcn-qucstion test
completes the program,

ADDSUB- addition and
subtraction with three levels of
difficulty. Again, wrong answers
arc followed by an explanation.

DIVISION- with five levels of
difficulty. Mistakes are explained
graphically, and a running score is
displayed.

SPELLING -up to 500 words
over five levels of difficulty. You
can even change the words yourself.

Cassette 3 -Business and

Household

For ZX81 (and ZX80 with 8K
BASIC ROM) with 16K RAM pack

TELEPHONE - set up your own
computerised telephone directory
and address book. Changes,
additions and deletions of up to
50 entries are easy.

NOTE PAD -a powerful, easy-
to-run system for storing and
retrieving everyday information.
Use it as a diary, a catalogue, a
reminder system, or a directors

BANK ACCOUNT -a
sophisticated financial recording
system with comprehensive
documentation. Use it at home to
keep track of 'where the money
goes,' and at work for expenses,
departmental budgets, etc.

Cassette 4 -Games

ForZXSl (and ZX8Q with 8K
BASIC ROM) and 16K RAM pack

LUNAR LANDING-bring the
lunar module down from orbit to a
soft landing. You control attitude
and orbital direction -but watch the
fuel gauge! The screen displays your
flight status -digitally and graphically.

TWENTYONE -a dice version
ofBlackjack.

COMBAT- you're on a suicide
space mission. You have only 12

missiles but the aliens have
unlimited strength. Can you take
12 of them with vou?

SUBSTRIKE- on patrol, your
frigate detects a pack of 10 enemy
subs. Can you depth<harge them
before thev torpedo vou?

CODEBREAKER-the
computer thinks of a 4-digit number
which you have to guess in up to 10
tries. The logical approach is best!

MAYDAY - in answer to a distress
call, you've narrowed down the
search area to 343 cubic kilometers
of deep space. Can you find the
astronaut before his life-support
system fails in 10 hours time?

Cassette 5 -Junior

Education: 9-11-year-olds

ForZXSl (and ZX8Q with 8K
BASIC ROM)

MATHS - tests arithmetic with
three levels of difficulty, and gives
your score out of 10.

BALANCE -tests understanding
of levers/fulcrum theory with a
series of graphic examples.

VOLUMES -'yes* or W
answers from the computer to a
series of cube volume calculations.

AVERAGES -what's the average
height of your class? The average
shoe size of your family? The average
pocket money of your friends? The
computer plots a "bar chart, and
distinguishes MEAN from MEDIAN.

BASES -convert from decimal
(base 10) to other bases of your
choice in the range 2 to 9.

TEMP- Volumes, temperatures
-and their combinations.

Cassette 6 - Family Quiz

ForZXSl (and ZX80witfi8K BASIC
ROM) with 16K RAM pack.
Four different quizzes, each
consisting of 10 questions suitable
for the whole family. There's a
target time for each quiz, and at the
end you're told how long you took
to answer the questions - and how
many you got right. The quizzes
cover a range of topics - including
maths, English grammar, and
general knowledge.

How to order

Simply use the order form below,
and cither enclose a cheque or give
us the number of your Access,
Barclaycard orTrustcard account.
Please allow 28 days for delivery.
14-day money-back option.

ZX SOFTWARE

Sinclair Research Ltd,

6 Kings Parsdc, Cambridge,

Cambs., CB2 1SN. Tel: 0276 66104.

To: Sinclair Research FREEPOST, Cambcrky, Surrcy.GUlS SBR,

Please send me ihc items I have indicated below. Pttascprini

Qly

Code

Item

Item price

Tola I

21

Cassette 1 -Games

£395

22

Casscuc 2 -junior Education

&ft

2*

Cassette 5 ■ Business and Household

£195

2A

Cassette 4 -Games

£5.95

25

Cassette 5 -Junior Education

095

26

Cassette 6 - Family Quiz

&m

17

*8K BASIC ROM for ZX80

£19.95

IS

*16K RAM pack lorZXSl and ZX80

£29.95

•Post and packing if applicable

£2.95

Total/;

•Please add £2.95 to total order value only if ordering ROM and /or RAM.

I enclose a chcquc/PO to Sinclair Research Ltd fot£

Mease charge by Access* Barclaycard/Trustcard no.

I 1 I '''''' I— I I L_L

J_L

'Phat<d{ituasappllc&bU.

Name : Mr/Mrs Mis\
Address: ! J L

I I I t I I 1 1_| I I 1 I I I

J I I L

J_J I_I I I I L

U I I ! 1 I I I I'l 1 I I [ | | | ISOF08 J

LEADERS IN COMPUTER GAMES

ZX-81

FIRST CHOICE FOR ZX: SUPPORT:

ZX-80

QS DEFENDER.

UP - DOWN - THBUST- FERE
First and orUy full screen display.
Software to drive QS SOUND BD.
Moving Planetary surface. Up to
84 fast moving characters on
screen at once. On screen scoring.
Ten missiles at once. Increasing
attack patterns. Requires 8K
ROM, and 4K mln of RAM. &5.80.

QS SOUND BD.

A programmable sound effects
board using the AY-3-89 10. 3
TONES; 1 NOISE; ENVELOPE
SHAPER: + TWO 8 BIT I/O PORTS.
Easily programmable from
BASIC, the AY chip does most of
the work leaving your computer
free for other things. Signal 0/P
via 3.5 mm Jack socket Ports 0/P
via a 16 pin I.C. Socket. &86.00.

QSCHBSBD./

A programmable character
generator giving - 128 SEP-
ARATELY PROGRAMMABLE
CHARACTERS. ON/ OFF SWITCH.
IK ON BOARD RAM. Enables
creation and display of your own
characters to screen or printer.
Demo cassette of fast machine
code operation routines and lower
case alphabet included. See below
for ZX PRINTER listing. £86.00.

P5 - LOueR case

Abcdetghi jkianopqrstuvwxHZ

K/yy

qs rrarvADERS.

LEFT - RIGHT - FIRE

13X7 INVADEBS; High score; 3

levels of play; RND saucers; Bonus

base; Drives Sound bd. & CHRS bd .

Requires 7K RAM. 8KR0M +S!ow.

&8.S0.

QS HI-BBS BD.

A Hi-res graphics board giving -
256 x 192 PIXELS. 6K ON BD.
RAM. SOFTWARE SELECT/
DESELECT. MIXED TEXT AND
GRAPHICS. 2K ON BOARD ROM.
Resident fast machine code
graphics software (in ROM)
provides the following HI-RES
Commands. - MOVE x, y; PLOT x,
y; DRAW X, y; BOX x,y; UP; DOWN;
LEFT; RIGHT; PRINT A$; SCROLL;
BLACK; WHITE CLEAR COPY. See
above for ZX PRINTER listings
using COPY. &85.00.

QS ASTEROIDS

LEFT - RIGHT - THRUST - FIRE
Software to drive QS SOUND BD.
Multiple missiles firing in 8
directions. On screen scoring.
Increasing number of asteroids.
Full mobility of ship to all areas of
the screen. Two asteroid sizes.
Bonus ship at 10,000 points.
Requires 8K ROM, 4K min of RAM
+ SLOW function. AS. SO.

QS3KRAMBd.

An extremely reliable static RAM

Bd. which combines with the

computer's memory to give 4K

total. Plugs direct in to the rear

port on your ZX Computer.

618*00.

QS MOT HER BOARD BD . & QS
CONNECTOR

A reliable expansion system
allowing a total of any RAM pack
plus two other plug in boards to be
in use at once. On board 5V
regulator drives all external
boards. Fitted with two 23 way
double sided edge connectors.
Connector is 2 x 23 way edge
conns soldered back to back.
Expansion can operate In two
ways - ( 1 ) COMPUTER <-►
CONNECTOR *-> Any QS add on bd.
(but no extra RAM pack). (2)
COMPUTER <-> CONNECTOR ~
MOTHER BD ^ ANY RAM PACK.
( 2 bds to fit in mother bd. ) Mother
board A 18.00 Connector A4.00.

Special offers & news

C 1 ) QS Mother bd, + connector + CHRS bd +The special Graphics version of

abctic computing's zx chess i i . *4s.oa

The strongest chess program with 7 levels of play.

OO QS MOTHER BD +CONNECTOR+either SOUND or CHRS bd. £40. 00.

We will be at the following shows . . . Come and see us . . .

THE COMPUTER FAIR, Earls Court, 23rd to 25th April

3rd ZX MICROFAIR, Central Hall, Westminster.

30th. April & 1st May

POSTAL AlflD MONEY ORDERS TO: ALL PRODUCTS FULLY GUAHANTED.

QUICKSILVA: 98, UPPER BROWNH ILL RJ>. : HATBUSH : SOTON : HANTS : ENGLAND.
Please state Type of machine. Which ROM, Memory size, when ordering.

THE
PROFESSIONAL

ZX81 KEYBOARD

All -you -need Keyboard Kit £28.95.
Case only £15.00.

All prices inclusive of VA T, postage and packing.
Please allow 21 days for delivery.

Plug in — no desoldering.

Space bar linked to space key.

Full travel keys. Six spare keys for
your own use.

Case available to hold keyboard and
ZX81 microcard.

, ■ 16K RAM pack clamp

supplied with case to
-*\ eliminate white outs!!

COMPUTER KEYBOARDS DIV.
DEAN ELECTRONICS LIMITED

GlendalePark FernbankRoad Ascot Berkshire England
Dial -a-leaf let 03447 5661 Telex 849242

EDUCATIONAL COMPUTING

on the

X81

co'tection

of fo$$omuchi
torso Uttk j

AM programmes
tit 1K

Creative use
graphics

of

Many innovative
ideas

Futty documented

inciudes many
games

A mi of proQtmmmm* to turn your
ZXM1 into « pomoetul ooXtcmtionl tool,
donl mvon need to know progrmmmjng,
Thwto **• ctoat instructions snd p4onty of r/pj
I Mfvto*. O+nJgrtd to go bmpond oViti M pemctico

'• loo m ing throu&i kitorocUon & d ¥#Co wfy»

Includes .-
TORTOISE
A simplified
version of the
famous Turtle
programme

COOED M/SSiLE
Combines the
fun of arcade
games with
learning

PROGRAMMES

PRIMARY
EDUCATION.

£4.95 only

_____ inel. p & p

fraph -plotter # Histogram # Simon -spell • Skeiehboard # Times-table # Sets
Series -qu<2 • XY- coordinates # Count • Equations # Areas • Guess -a -Volume
Angles • Upstairs- Dow rma tt $ • Music* notes • See -saw • Wipe -out •Spe*
Temperature • Clock # Money • Snake
Mastermind • Number - shoot • +26 more

| j 0: (Please send me copies Educate 's 5(X|

EDUCARE 1 1 enclose cheque/postal order for £ ....■

I 139a Sloane St. ^ ame I

•£& |>«^~;~:z,:n..zz::r:rr:j
I fc .™ = .^..^. = .^.^. == ..j

EDUCARE

THE PERSONAL
COMPUTER BOOK

new edition just published
by Robin Bradbeer

co-author of best-selling
BBC Computer Book

The Personal G
Computer Book

"*" by RobJr Brodbc^r

Buying your own micro?

Then you need Robin

Bradbeer's Personal

Computer Book. It tells you

all you need to know about

personal computers and

includes an illustrated

up-to-date survey of 60

micros available in the UK. It contains

information on what you can do with micros,

details of your nearest computer club and a

survey of books and magazines. Only £5.95.

Available from W.H. Smithand leading booksellers, ordirect
from the publishers by sending £6.95 (including postage
and packing) to Virginia Ayers, Dept. YC, Gower Publishing
Co Ltd, Gower House. Croft Road, Aldershot, Hants GU 1 1 3HR.

92 YOUR COMPUTER, JUNE 1982

:

MICHAEL ORWIN'S ZX81 CASSETTES

CASSETTE ONE for 1 k ZX81

"I had your Invaders/ React cassette ... I was delighted

with this first cassette."

P. Rubython, London NW10.

"I have been intending to write to you for some days to

say how much I enjoy the games on 'Cassette One'

which you supplied me with earlier this month. Please let

. . . into the secret of your first time load every time!"

E.H., London SW4.

Just two out of over 30 unsolicited testimonials.

Cassette One Ik machine code programs:

React, Invaders, Phantom aliens, Maze of death. Planet

lander, Bouncing letters, Bug Splat. 1k Basic programs:

I Ching, Mastermind, Robots, Basic Hangman PLUS

Large screen versions of Invaders and Maze of Death,

ready for when you get 16k, Cassette One costs £3.80.

CASSETTE THREE

8 programs for 16k ZX81

CASSETTE TWO

Ten games in Basic for 16k ZX81

Cassette Two contains Othello, Awari, Laser Bases,
World mastermind, Rectangles, Crash, Roulette,
Pontoon, Penny Shoot and Gun Command.
Cassette Two costs £5.

S TARSHt? 7RQJAN

Repair your Starship before disastor
strikes. Hazards include asphyxiation,
radiation, escaped biological specimens
and plunging into a Supernova.

STARTREK This version of the well known Space
adventure game features variable Klingon mobility, and
graphic photon torpedo tracking.

PRINCESS OF KRAAL An adventure game. .

BATTLE Strategy game, for 1 to 4 players.

KALABRIASZ World's silliest card game, full of pointless

complicated rules.

CUBE Rubik Cube simulator, with 'Black step' facility.

SECRET MESSAGES If you are spying for the KGB, why
not throw away those incriminating code books, and buy
this innocent looking cassette? This message coding
program is txlp qexi jf .

MARTIAN CRICKET A simple but addictive game (totally
unlike Earth cricket) in machine code. The speed is
variable, and it can run very fast.
Cassette Three costs £5.

Recorded on quality cassettes, sent by first ciass post, from:
Michael Orwin, 26 Brownlow Rd., Willesden, London NW10 9QL (mail order only please)

MIND YOUR LANGUAGE

...it's computer language ware talking about.
Getting people to understand it is hard enough— but
getting computers to understand our language...!
We've got two features on aspects of computer
communication -plus reviews of Pearcom
(an Apple lookalike) and two powerful business
machines, a description of how a garage
computerised its business...

...and that's just a sample of Practical Computing,
together with advice for users of Pet, Apple,
Tandy and Sinclair ZX 80/81 computers.
Buy Britain's leading personal computer magazine.

JUNE ISSUE ON SALE NOW

80p AT YOUR NEWSAGENTS -BUT HURRY

YOUR COMPUTER, JUNE 1982 93

178 West St, Sheffield SI 4ET. Tel.(0742)755005

ACORN

VIC 20

ACOM ATOM K>^&f(r**iPS.U, Br COlOUR BOARD 1»£0€

ATOMOtftt'AOC.ttKStflCLCOtSKOftfVL mQOC

ATOM COLOUR BOARD..... »OQC

ATOM CAM|$ JACK 1.11 10 WA

•Mil

WORD PACK ACM MOOA

FORTH 10 0OA

FORTH THEORY 6> PRACTICE..,..* IfM

BUSMESS .. 10.00A

8US*iESSS00< .... tttOA

SVNTHfSlSCR ...... 10«A

utepackace iojOOa

OtSftOtARV ........ 10»A

DATABASE., SOjOOA

UTiUTYPACltt...... IQttA

SOFTV.0.U 10J0OA

PEEKOCOMPUTfR 100OA

MATWS PACKS »*« 1000

«Mh

WORD TUTOR 1000A

ADVENTURES , WOOA

ATOUCtiESS WOO*

FlOATISiO PC4HT « ov . ao 00A

8 0CRQMPAC*. PWOKE

UA&/CROO* . 7JB»

ft ■ c bas>c programmes B00< fJB*

VtC 20 COMPUTER, . .. PHOtH

VK CASSETTE 0«K »0*O

VKPRWTBt 200 Wt

SVfGLf D«KDR*«.... 3*4 Jtt

PROGRAMMER* AJO CARTRIDGE *>»•

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VttPROGRAAIMERS REFERENCE GUIDE 14*8

V»C GAMES ROMS, VARIOUS FROM 17JU

CASSETTE SOFTWARE

PACK MAN fhigMwdhitionk. M$A

SUBMARINE. . 7JMA

GUNMAN Ifcafc m&kiDort 730A

NAVAt. BATTLE ., 7J0A

SPACE WVAOfRS... 7J0A

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CRAZY ftAUOON. 7B0A

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BAUOONtOMBER TJOA

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TR|ASU*t CA**YiSG 7 BOA

SURER MOON LANDER 7J0*

SVOTMACMMt 7WA

SHARP

VIDEO GENIE

'77,

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Postage Rates

a.75p b.1.00c.1.50d.2.50e.5.00

MAILORDER

ALL PRICES
EXCLUDE VAT

Pncas and offers were prepared many weeks before pub'.»cation of this
magazine, and whilst every possible effort will be made to meet our offers, in
some esses prices may fluctuate and we would advise you to confirm by
telephone before ordering.

Please Supply.

Access/ Barclay/ Cheque

Card No

L_— — — — —

P&P+VAT
_ Total

£
£
£
£
£
£
£.

Name

Address.

Code.

Tel

94 YOUR COMPUTER, JUNE 1982

ZX Users' Club

JOIN YOUR USERS' GROUP - AND MAKE TH
MOST OF YOUR MICROCOMPUTER

Join the National ZX80 and ZX81 Users' Club, by subscribing to the official monthly club magazine

INTERFACE.

{ ) Please send me the next 12 issues of INTERFACE, containing many programs for each machine in each
issue, plus hints, tips, software, hardware and book reviews, plus special offers for members. I understand
you will be able to help me with problems regarding my computer, and let me know of any local branches
of the club in my area. I enclose £9.50 (UK), £12.50 (Europe) or £16.00 (elsewhere).

Please send me the following books:

( ) GETTING ACQUAINTED WITH YOUR ZX81 - by Tim Hartnell - £5.95. This great 2X81 book contains
over 80 programs in its 128 pages. Takes you from the first steps of programming your ZX81 to quite com-
plex programs such as WORD PROCESSOR, DRAUGHTS and LIFE. You'll find a host of programs to get
your ZX81 up and running with worthwhile programs, right from day one. Other programs include SPACE
BOY, ROLLER-BALL, CHEMIN DE FER, GRAFFITI, MICRO-MOUSE, POGO, TOWERS OF HANOI,
BLOCKOUT, SALVADOR, BANDIT and DODGE CITY.

As well as programs, there are sections to explain the use of PLOT, UNPLOT, PRINT AT, MAKING THE
MOST OF 1K, ARRAYS, WRITING PROGRAMS, BIO-RHYTHMS, ARCADE GAMES, RANDOM
NUMBERS, PEEK AND POKE, HOW TO CONVERT PROGRAMS, USEFUL ADDRESSES, SPECIFICA-
TIONS, THE NEW ROM.

( ) THE GATEWAY GUIDE TO THE ZX81 AND ZX80 - by Mark Charlton - £6.45. Explains ZX BASIC from
first principles. 180 pages, more than 70 programs Recommended by Creative Computing.

( ) MASTERING MACHINE CODE ON YOUR ZX81 OR ZX80 - by Tony Baker - £7.50. Warmly welcomed
by the computer press, this book has continued to attract praise, because it does exactly what it claims to
do in the title.

( ) 49 EXPLOSIVE GAMES FOR THE ZX81 (and 29 for the ZX80) - edited by Tim Hartnell - £5.95. Every
game you need: DRAUGHTS, GALACTIC INTRUDERS, STAR TREK. DEATH MAZE, 4-IN-A-ROW and
an 8K ADVENTURE-type program SMUGGLERS BOLD.

( ) 34 AMAZING GAMES FOR THE 1K ZX81 - by Alastair Gourlay - £4.95. All programs dumped from the
printer and guaranteed to run. This book is the key to making the most of 1K.

{ ) GETTING ACQUAINTED WITH YOUR VIC20 - by Tim Hartnell - £6.95. This book is the ideal one for
first-time users of the VIC 20, with over 60 programs.

{ ) SYMPHONY FOR A MELANCHOLY COMPUTER and other programs for the VIC20 - £6.95. A great col-
lection of 24 great games — all dumped direct from the printer - for the VIC20.

( ) GETTING ACQUAINTED WITH YOUR ACORN ATOM - by Trevor Sharpies and Tim Hartnell - £7.95.
< ) 39 TESTED PROGRAMS FOR THE ACORN ATOM (the best of INTERFACE) • ■ £6.45.
( ) PASCAL FOR HUMAN BEINGS - Jeremy Ruston - £6.45.

ATOM

INTERFACE, - fEA

44-46, Earls Court Road, Department YC, London W8 6EJ. \g I ■

Please send me the indicated items. I enclose £-

Name

Address

YC

YOUR COMPUTER, JUNE 1982 96

o

I

y

JTTj

dftronics zxso/si

4K GRAPHICS ROM

RMfl ="l\n9Tlo"|

s©=$k~ **-*■- II /
U=2+-x" * II C^ 1 i-fr" J

E± - |*F J V ^ AM* 1 11

Be

»

rt

■ »

• ■

SS

M ■■

5CEIRE

n.-»T

SOME OF THE GRAPHICS
NOW POSSIBLE ON THE ZX81

The dK Graphic module is our latest ZX81 accessory. This module, unlike most other accessories
fits neatly inside your computer under the keyboard. The module comes ready built, fully tested and
complete with a 4K graphic ROM. This will give you 448 extra pre-programmed graphics, your
normal graphic set contains 64. This means that you now have 512 graphics and with there inverse
1024. This now turns the 81 into a very powerful computer, with a graphic set rarely found on larger
more expensive machines. In the ROM are lower case letters, bombs, bullets, rockets, tanks, a
complete set of invaders graphics and that only accounts for about 50 of them, there are still about
400 left {that may give you an idea as to the scope of the new ROM). However, the module does not
finish there; it also has a spare holder on the board which will accept a further 4K of ROM /RAM.
This holder can be fitted with a 1K/2K RAM and can be used for user definable graphics so you can
create your own custom character sets. £29.95.

96 YOUR COMPUTER, JUNE 1982

HARDWARE/ SOFTWARE

ZX KEYBOARD

Now with repeat key and facilities to add numaric pad. The keyboard has all the 80/81 functions on
the keys.

The keyboard has been specially designed for the Sinclair computer and is supplied ready-built. It
also has facilities for 3 extra buttons which could be used for on/off switch, reset, etc. £27.95.
Numaric add on £10.

MEMORY 80/81

16K RAM MASSIVE ADD-ON MEMORY

for 80/81 ONLY £25.00

81 SOFTWARE

CENTIPEDE

This is the first implementation of the popular arcade game on any micro anywhere. Never mind your invaders,
etc., this is positively stunning, the speed at which this runs makes ZX invaders look like a game of simple snap.
£4.95.

3D/3D LABYRINTH

You have all seen 3D Labyrinth games, but this goes one stage beyond; you must manoeuvre within a cubic maze
and contend with corridors which may go left/ right/up/down. Full size 3D graphical representation. £3.95.

TOOL KIT

An extremely powerful tool kit for use with the 16K 81 uses 4K of memory space. £6.95.

GRAPHIC ROM SOFTWARE

Centipede. The graphic rom version of our popular centipede game. £4.95.

SPACE INVADERS

Is the only real version of space invaders on the ZX81 . £4.95.

ASTEROIDS

New for the Graphic Rom, a brilliant version of the arcade asteroid game. £4.95.

cK'tronics

23 Sussex Road, Gorleston,
Great Yarmouth, Norfolk.
Telephone: Yarmouth (0493) 602453

YOUR COMPUTER, JUNE 1982 97

* REQUIRE 16K RAM

PHIPPS ASSOCIATES

(Mail Order DeptB)
99 East St, Epsom Surrey, Tel 03727 21215

quoting your credit card N°j 24hr phone servic*
Air Man "Euro pe plus 70 p Elsewhere plus £1.70 J

miCRQAGE ELECTROniCS

LONDON'S BIGGEST ACORN STOCKIST

ATOM KITS

In our books the best computer

kit available. Build yourself

an Acorn Atom for only £135.

plus £2.50 p+p

New Software from Acornsoft.
Come and get them all including
Atom Chess • Desk Diary •
Adventu res • I n teractive Teach ing ♦
FORTH *Atomcalc ©Database
LISP • Game Packs 1 — 11*
From £11.50 + 30pp&p

BBC ROM

Update your Atom to the BBC
operating system.

Atom Discpack. £345

5 l A discpack only £345, operating
manual, cables, plus £2.50 p+p

The BBC Cassette Recorder £28
As chosen by the BBC, but
cheaper? £2.50 p+p

OFFICIAL

OUJB
STOCKIST

Working BBC
machine in stock. Call
in for 'hands - on' experience.

ORDERS TAKEN NOW

THE GP - 80A dot matrix printer.
LOWEST EVER PRICE

ONLY £199 £4.50 P + P

Dot Matrix, Full 96 ASCtl
character

New! Just arrived.
The fantastic GP100A
printer. Full printing width.

ALL PRICES INCLUDE VAT
ABSOLUTELY NO MORE TO PAY.

FROM THIS TO THIS

AT THE FLICK OF A SWITCH

With the new ZENITH Monitor. Choose between small or large format
depending on what you're doing. Smalt format for definition,
large format for display. Full 12" GREEN screen. Only £85 while
stocks last. It doesn't change the output from your computer, just
changes the size of the display. Ideal for VIC 20, TRS 80, Atom,BBC,
+ Genie machines. £4.50 p+p

Blank

Cassettes

40p each,

£3.50

for 10.

70p p+p

Also available:

2114 IC's, Paper for most
printers, Enormous selection of
Books, Leads, etc, etc, etc.

RACOMM COLOUR MONITOR

Absolute high resolution. 700x300
pictais 12" £350 + £5 p+p Atom
BBC, & Genie machines.

DAI Personal Computer. £684
48K RAM 24K ROM

If it's not in the advertisement,
send for our mail order lists.

We accept company/
institutional orders.

miCFTOGE ELECTRDniCS

135 HALE LANE EDGWARE MIDDLESEX HA8 9QP
TEL: 01 959 7119 TELEX 881 3241

98 YOUR COMPUTER, JUNE 1982

30+ PROGRAMS

FOR THE

BBC MICROCOMPUTER

This Book contains program listings, with explanations and tips

on using the BBC Micro

GAMES UTILITIES EDUCATIONAL GRAPHICS a MUSIC

ASTRO RUN' 'SCREEN PLAY' '3D GRAPHICS' . . .

Most programs will run on Models ABB

Edited by C.J. Evans, various Authors, April 82

£5.00 inclusive of p€rp

CARRYING CASES FOR MICROS

Rbreboard cases for: 2X81: BBC Micro: Acorn

Atom: Vic: Apple: 2 Apple Disks: Atari 400 or 800 £18.50 pap £2.50

For ZX81 only, COMPACT BLACK A8S CASE £21.00 pap £2.50

Cases are foam padded with cutouts for: Micro, PSU h Cassette Recorder.
2X81 Cases also have room for RamPack & Printer. Apple cases have room
for Micro only. Fibreboard cases can be supplied modern suitcase style or
robust old fashioned style with strengthened corner pads.

Cassette leads for the BBC Micro
The BBC Micro comes with an incomplete lead

7Pin Din to 7Pin Din £4,65 p&p 35p

7Pin Din to 5Pin Din & 2,5mm minijack £4.65 pap 35p

7 Pin Din to 2 x 3.5mm a 1 x 2.5mm minijacks £4,65 pap 35p

7Pin Din PLUGS Two for £0.65 pap 35p

PRINTER CABLE (Centronics type) £17.00 pap 50p

RAM CHIPS

4816 As used in the BBC Micro 8 Chips gives 16k £5.00 each

21 14 As used in the Acorn Atom 20 Chips gives 10k £1 .30 each

6116 As can be used to replace the Ram chip

inside the 2X81 to give 2k internal Ram £7.50 each

p&p Ram chips 50p per order

Programs & Hardware designs for the BBC Micro wanted.

VAT INCLUDED WHERE APPLICABLE

Send $A£ for full Price List

C.J.E.

microcomputers

25 HENRY AVENUE, RUSTINGTON,
W. SUSSEX BN16 2PA (09062) 74998

ZX81 ADVENTURE SPECIALISTS

C2: VOLCANIC DUNGEON/HANGMAN £4.50

A) VOLCANIC DUNGEON: Rescue if you can, the Elfin Princess.
Mythical monsters, pits, firey caverns, diminishing strength and water
make your quest anything but easy.

FULL 16K PROGRAM" SAVE GAME ROUTINE" SINGLE KEY ENTRY"

"Volcanic Dungeon is terrific value and I would recommend it to
anyone." Mrs. Thomas, Cornwall.

B) HANGMAN: Deluxe version of the classic game. Play against 3n
opponent, or the computers 400 word vocabulary. Good graphics.

C3: ALIEN INTRUDER/HIEROGLYPHICS £5.00

A) ALIEN INTRUDER: You awaken to find you are the only survivor on
the Explorer Ctess 3 Starship. Can you escape before you also fall
victim to the Alien monstrosity that devoured the crew? There are
many ways to end this adventure but only one way to survive!
FULL 1$K PROGRAM** INTERACTIVE GRAPHICS**

SAVE GAME ROUTINE-*

B) HIEROGLYPHICS; Decode the ancient 39 symbol alphabet in time to
save the famous explorer, "Wullie Makeit" from a sandy grave.
FULL 16K PROGRAM** ANIMATED GRAPHIC DISPLAY**
RANDOM CODE*"

C4: WUMPUS ADVENTURE/MOVIE MOGUL £5.00

A) WUMPUS ADVENTURE: FOR 1 TO 4 PLAYERS! Seek the famous
creature in the most dangerous Wumpus hunt ever. All the usual
features are there SUPERBATS* PITS* TREMORS* SWAMPS*
MAGIC ARROWS**

PLUS Exciting new features: EVIL GOBLINS that will try to sacrifice

you to the Wumpus. GIANT SERPENTS* WUMPUS MUCK* MAGIC

SPRINGS**

FULL 16 PROGRAM** RANDOM & PRESET CAVE PATTERNS**

YOU CONTROL THE LEVEL OF DIFFICULTY** GREAT FUN FOR

YOU AND YOUR FRIENDS**

B) MOVIE MOGUL: Guide your film through the often hilarious traumas
of production. Use your budget wisely and you may make a fortune.
Success depends on many factors and not just luck.

FULL 16K PROGRAM*'*

ORDERS: Plus 50p P&P or targe S.A.E. for list to:

CARNELL SOFTWARE,

4 STAUNTON ROAD, SLOUGH, BERKS. SL2 1 NT.

The above arc also available from:
BUFFER MICROSHOP, STREATHAM, LONDON.

OAKLEAF COMPUTERS ltd

Education Hobbyist A Small Business Computers

wtv- wmw o ir

*5<*!^« H*V\ W17V

ITS NOT JUST
ACORNS THAT
LOOK BETTER ON AN

OAKTREE
WORKSTATION

THE UNIT SUITS BBC

A&B APPLE PET ZX81

VIC 20 TRS80 ETC.

^ *JUST RELEASEI

TWIN USER JOYSTICK INTERFACE

£12.95 ALL INCLUSIVE

Protect tho keyboard of your fully expanded Atom by interfacing Atari joysticks

to it. The joysticks pfagi into tho interface which in turn simply plugs to the 64

way bars, (available at i 3. 99 inc. if ordered with the unit}. Now two peop'e can

successfully play games or one person can have more control over the Atom.

Full software supplied. Some conversions are given for the more popular

Atom software packages including Bug Byte, Program Power

and Acornsoft.

With a built in accessory

drawer, this smart unit turns

your set up into a

professional and business-like

system. The drawer holds up

to 50 diskettes or your tape

collection and leads etc.

Otdm try tete&hoae QvQtrtg
YOUf csr tf nvm&tf cr writ*

£19.95

121 DUDLEY ROAD, GRANTHAM, LINCS NG31 SAD
Tel: (0476} 76994

WORN

SPECJAUSTS

BBC SOFTWARE

Wordwisc

The Word Processor for the BBC Micro Computer.

Word processor for the Model B Micro. Supplied in
ROM and therefore leaving about 27K for text, over 4000
words. All the usual word processor features plus several
unusual ones like a fully automatic word count. Available
soon for £65.00 + £1.50 p&p + VAT. Ask for leaflet
describing WORDWISE in more detail.

RAM UPGRADE kit to increase Model A to 32K RAM.
Run Model B programs and graphics. Supplied with
instructions — around £30.00 +■ VAT. Phone or write for
latest price and availability.

CASH waiting for any good programs to add to our
range. We pay excellent royalties or cash.

OMPUTER
ONCEPTS

DEPT YC1
16 WAYSIDE
CHIPPERFIELD
HERTS WD4 9JJ
(09277) 62955

YOUR COMPUTER, JUNE 1982 99

HILDERBAYLTD

PROFESSIONAL SOFTWARE

If you don 't believe that the Sinclair ZX81 can do real work,
come and see usat the Computer Fair Exhibition. Earls Court
(23rd-25th April) and the ZX Micro Fair. Central Hall ,
Westminster. London SWl (30th April-lst May).

ZX81 & 16K SOFTWARE: Reviewed in "Your Computer" (Feb. 1982).

* Payroll for up to 30 employees. Meetsall regulations £25.

* Stock Control Fast, big, and versatile £25,

* Budget n 5

* Critical Path Analysis Up to 500 act ivities £ 1 5.

* VAT & Mortgage & Loan £8.

* GOLD: A really good adventure; together with the intriguing
"PiekaWord'\£a

* RELIABLE 16K RAM Pack for the ZX81 £42.

* BEAMSCAN: Beam analysis for architectsand engineers £25.

* APPLE II Payroll: £35.

* HEWLETT PACKARD 9845B: Super spline (general purpose
interpolation and tabulation).

* MEMOTECH 64K Memopak £ 79.

DO YOU HAVE DIFFICULTY LOADING TAPES! V\fe have the answers:
and for well under £ 10.
Contact us for more details.

CROFTON PROFESSIONAL KEYBOARDS, MONITORS. VDU*$
Prices include VAT. Post & Packing. COD Orders £2 extra.

TAPE H INT: Don't use the first 20 seconds

of your cassettes — most tape problems

are found near the ends of the tape.

HILDERBAYLTD

8/10 PARKWAY, REGENTS PARK
LONDON NW17AA

Enquiries for Hilderbay Ltd. will now be handled
by HOLDCO LTD. TeL 01-251 3090

ALSOONZX81 + 16K

Financial Budget/ Cash Flow Forecast; The program
allows thirteen columns (12 months + total). The forecast
can be changed and a "WHAT IF?" possibility can be ex-
amined on the screen. £25.

Sales Day Book: keeps a record of ail invoices, with nett,
VAT zero rated and total. £18.

Purchase Day Book: keeps records of all purchases and
VAT £18.

Petty Cash Book: Keeps a record of all petty cash ex-
penses and allows for VAT to be calculated from total if
unknown. £18.

Cash Sales Day Book: as sales day book but with the addi-
tional "Method of payment 1 ' feature, incl. cash, cheque,
postal order, Access, Barclays, sundries and unpaid. £18.

Cassette Recorders: individually tested for ZX81 and sup-
plied with a test tape for loading. £22.

Barcharts for Architects: a simplified version, takes away
the tedious task of manually handling the problem £25.

Bank Account: calculate your bank charges whilst keep-
ing your account £5.

Architects Programs: Barchart with S-curve/Dewpoint
calculations N.B.S. on computer/Structural programs/etc.
etc.

All programs now also available for ATARI and SHARPE

HOLDCO LTD.
14, BRITTON STREET
LONDON EC1M5NQ

Tel: 01-251 3090

M'mmwmMmMt

for

ZX8I

ZXS0

TRS80

iDF.O GF.SIE

• AS MANY SEA SO NS AS YOU LIKE *4 MVISIOSS*

*PHOMOTtOS 6 RELECATffiSlT

*FULL LEAGUE TABLE S *

* TRANSFER MARKET*

*TS7lRlES*~

• 7 LEVELS OI PLAY -k

^iTSA VE GA MEFACIU TY *

• MA ,XA GERIA L RA TLXG •
*PKK YOUR TEAM FOR EACH MATCH * F.A. CUP*

1LI.LUAIU.LLU IT IJ

this, is NOT j men- simulation. I his is an exciting and hijjhlv vnjovjbk*

•sum- in which um plj> Ihtr pari of a Foolhall Manager ctipini; wild Ihc

proMcms and decisions in v oh id in running >our club. I here arc so many

fealurcs ti is impossible lo list ilu-m here bul included are form (lop

teams NOKMAE.l.Y *in), ^iani-killings, u^r bills lo pa>, and >ou ean

even be sacked! It is a game requiring a great deal of \kill, and people

pla> it lot literal! v hours on end <ue ha*e proof!).

WE GUARANTEE that Ibis is one of the best computer games >uiTvc

ever pi.i.w-ii:

Bl"l B EW ARE, Ibis g ame is extremely addictive!

FOOTBALL MANAGER

IS SUPP1 Ji.D MIIH f\$TRUCriO\S
- OCCUPIES THE EST! RE MA it A St

HARDWARE REQUIRED

7X8!/
ZX80

I6K RAM

THSS0/
Video Genie

LEVEL! I
16K RAM

to Ostk-f w<f Cttet/wtKO for £7.95

tiMt<r/m-M> u>. AimtCm E CAMES

utlHpt, Y.C. I'M. fax 27$

COWWtKKOH

Vf/y ro\ KEiWES VKI4 ?\E

/7/.-IS-/. SlAtLiOMPUILR

COLOUR OSS A MX!

From £M$4)1)(S& (Graphics)

Now you can add a coloured background to your
displays with high quality P.V.C. in either blue or

green,

ONLY £2-95+ p.p. per pack*

* No loss of clarity

* Cuts eye strain considerably

* Easily removed

* Strong flexible P.V.C.

* Each sheet measures 15" x 12" (Larger sizes

available on request)

* Fits most b/w TV's up to 19" screen

* Full instructions provided

Send cheque/P.O. to:-
Ellanbee (Graphics)
MICHAEL HOUSE, NORTH BURNS
CHESTER-LE-STREET
CO. DURHAM DH3 3TF
Tel; (0385) 886987

* Pack contains 1 Blue & 1 Green

Please allow 28 days for delivery
Postage & Packing 0.55p *

100 YOUR COMPUTER, JUNE 1982

: _

ZX81/ 16K SOFTWARE

NEW!! NEW!! NEW!!

ARCADE GAMES!

"SPACE- INVADERS"

Simply the best yet, the closest thing to real Space
invaders on the ZX-81 including 1 or 2 player option and
software to drive the OS-character board for real!
invaders.

"STARTREK"

16K STARTREK: Exciting space adventure game
~ including ktingons starbases, phasors, 8x8 galaxy,

4-levels of play, long and short range scanners, etc.

"SUPER-WUMPUS"

16K SUPER-WUMPUS: Can you hunt and catch the
— ---■ mysterious wumpus in his underground labyrinth?

Intriguing underground adventure.

"GRAPHIC GOLF"

16K GRAPHIC GOLF: Test your golfing skills on
SILVERSOFT'S 18-hole golf course. Many hazards
including lakes, trees, streams, rough, etc.

"GAMES PACK 1

§§

zzzz 16K GAMES PACK 1: Fantastic value for money,

nearly 50K of programs on one cassette. Five games
including "Real Time Graphic" Lunar Lander, Starwars,

~ :r Hammurabi, Minefield, Mastermind.

"3D-MYSTERY MAZE"

|= fj 16K 3D MYSTERY MAZE: Amazing three dimensional

-- maze. Walk through the maze in 3-dimensions, ultra-

'JZ~ fast machine code display, hundreds of different mazes.

S "ZXZOMBIES"

Can you escape from the man-eating zombies by lead-
itn-* i ing them into the pits? 8-levels of play, increasing

difficulty.

"ASTEROIDS"

Authentic representation of the arcade game with left,
right, thrust h fire controls, 5- levels of play 6t alien
spaceships.

"DROPOUT"

Can you stop the aliens from building up in their launch
chutes before they drop down €r destroy you. Exciting
arcade game.

Cheques/ POs payable to "SILVERSOFT".

Prices Asteroids & Dropout £5.95 each

The rest £4.95 each

Two or more deduct £1 .00
S.A.E. FOR CATALOGUES

Name.

Address,

ZX8T, VIC-20 & BBC SOFTWARE WANTED
EXCELLENT ROYALTIES SAE FOR DETAILS

.YC5/82

SILVERSOFT (Dept. YC)

40 Empress Avenue, Hford, Essex.

Tel: 01-518 0877

BDOD BAUD FDR SH5I

FAST RELIABLE PROGRAM STORAGE FOR THE
ZX81 IS NOW HERE. THE L.E.S. FAST
TRANSFER SYSTEM OPERATES AT OVER 6000
BAUD USING ANY GOOD QUALITY AUDIO
CASSETTE FOR PROGRAM STORAGE. THE

F.T.S. PLUGS INTO THE EXPANSION PORT BUT
DOES NOT INHIBIT THE USE OF RAM PACKS
ETC. SOFTWARE IS ON BOARD TO OPERATE
OUR EPROM PROGRAMMER. AS EASY TO USE
AS A CASSETTE RECORDER.

Inclusive price £99.50 (Discounts for Schools/Clubs
. . . Write for details)

<

EPROM
PROGRAMMER

Programs 2716, 2732 and
2764 Eproms under soft-
ware control. Software is
on board the F.T.S. or is
free on a cassette at
standard speed.

Built £42.00 Incl.

Kit £35.00 Incl.

EPROM BOARD

Takes 4 x 2716 Eproms.

Switch selectable.

Kit only £1 0.00

MOTHER
BOARD

Fully buffered and
equipped for up to 6
expansion boards.
Auxiliary 5 volt regulation
is required. Built only*

Withreg £35.00 Incl

Without £33.50 Incl

LfinSODLUriE Electronic Systems

I UNIT 21 BOROUGH ROAD INDUSTRIAL ESTATE,
STEEPLEJACK WAY,

D A R LI N GTO N , f 4MHz z80 cpu E UROCA RD SIZE Wl TH S TD

CO. DURHAM, CONNECTOR Usual lines buffered, reset selectable

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YOUR COMPUTER. JUNE 1982 101

AUTORAM

The sole ZX81 agent for the
Arab World is interested in
software, publications,
add-ons, etc.

Don't miss this opportunity
- ACT NOW!

Send samples of all you have to:

P.O. BOX 147

JEDDAH, SAUDI ARABIA

Tel: 6604212

Telex: 402 276 AUTORAM S. J.

BEEBUG ffii
BBC MICRO

INDEPENDENT NATIONAL USER
GROUP FOR THE BBC MICRO

IF YOU'VE GOT A BBC MACHINE, OR HAVE
ORDERED ONE, OR ARE JUST THINKING ABOUT
GETTING ONE, THEN WE HOPE BEEBUG HAS SOME-
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BEEBUG provides a central information point for users
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We run a regular newsletter (10 issues per year)
devoted exclusively to the BBC machine.
New program listings in each issue (3-D Noughts and
Crosses, and full colour Moon Lander in the April issue).
Hardware hints and tips, How to decide between the A and
B options. How to upgrade the A option. Reviews of the
latest software. A series of articles on getting the most
out of your machine. How to add joysticks and games
paddles to both the A and B options. Software competi-
tion. A beginners guide to BBC BASIC starting in the
April issue. Discount software and hardware. Regular
advice clinic to answer your queries. Other projects and
activities in the pipeline, plus a host of ideas contributed by
members. Dr D E Graham,

Sheridan Williams

Membership: Q£\

Introductory offer: p,-»

6 months £4.50 £

1 year £8.50 St.

Make cheques payable to

BEEBUG or s.a.e. for further details

BEEBUG

PO BOX 50

St. Albans, Herts.

ZX 81 owners

Protos

Keyboard is here

At last! A real, full size keyboard In a top quality case for
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FULLY BUILT £64.95 inc. VAT

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• Key legends can be changed for future new ROM functions

• Sinclair PCB fully enclosed — and room for much more
If you feel you've outgrown your ZX-81 don't sell it for
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For details, large SAE, please. For orders add £2.80 post and
packing. Cheques to 'Frome Computing'.

Protos

Computer

Systems

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BA11 2SF

reprints

If you are interested in a particular article/special
feature or advertisement in this journal

HAVE A GOOD LOOK AT OUR

REPRINT SERVICE!

We ofter an excellent, reasonably priced service
working to your own specifications to produce a
valuable and prestigeous addition to your
promotional material. (Minimum order 250 copies).
Telephone Michael Rogers on 01-661 3036 or
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To; Michael Rogers, Your Computer, Reprint Depart-
ment, Quadrant House, Sutton, Surrey SM2 5AS.

I am interested in copies of article/advert.

headed . featured in this

journal on pages , . . , issue dated

Please send me full details of your reprint service by
return of post.

Name . . . .

Company * . ,

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Tel No

102 YOUR COMPUTER, JUNE 1382

PUT YOUR

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Both RAM packs use seme neet btack ASS plastic cere (on/y 27 x 47 x 7$ mm. /

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Cssserte and instructions ........... , £690

ZX$1 MULT1GRAPHICS U6k R/WneededY create drawings, advertising displays etc on
screen. Numeroue printing style* including lower case. Displays may be SAVEd on tape,
printed on you* ZX Printer Cateette and 20 page Manual £4.50

2X81 tk GAMES 15 real-time and educational garnet)
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ZXSl Ik GRAPHICS (Kaleidoscope, Large Pnm, Medium Print Draw A Picture)

Cassette and >tftructton* . £3,00

Manual onry (12 pages containing accurate listings, notes, information and idea*) . , £3.00

Package of cassette and Manual £4.50

2X81 Ik STATISTICS {4 program* of descriptive and Weremial nstisticaJ

Cassette and instructions , . , £3,00

Booklet iS pages containing lutings, test date etc.J £2.00

Cassette and booklet . £4,00

2X60 software also available

Prices all-inclusive in British Isles

European customers please add 30p per software rtem; worldwide 70p\

Overseas customers write for detais of hardware mailing charges.

BRIDGE SOFTWARE (Y) «**«*»**»•
5 36 FERNWOOD, MARPLE BRIDGE, STOCKPORT, CHESHIRE SK6 5BE
JT Send s.e.t. for detaSs

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YOUR COMPUTER, JUNE 1982 103

Wherever you are
in theUK there's a

Genie dealer nearby

DTmriYrmmm^mYf act mum mmtttM t\ ^F

Genie I & n Approved Dealers

AVON Microstyle, Bath, 0225 334659/319705. BEDFORD

Comserve, Bedford, 0234 216749, BERKSHIRE P.C.R,

Reading, 0743589249. Castle Computers (Windsor),

07535 581 15. BIRMINGHAM Ward Electronics,

Birmingham, 021 554 0708. Consultant Electronics,

Birmingham, 02 1 382 7247, A. E. Chapman and Co.,

Cradeley Heath, 0384 66497/8. BUCKINGHAMSHIRE

Photo Acoustics, Newport Pagnell, 0908 6 10625.

CAMBRIDGESHIRE Cambri dge M icro Computers,

Cambridge, 0223 3 14666. CHESHIRE Hewart

Electronics, Macclesfield, 0625 22030. Mid Shires

Computer Centre, Crew, 0270 21 1086. CUMBRIA

Kendal Computer Centre, Kendal. 0539 22559. DORSET

Blandford Computers, Blandford Forum, 0258 53737.

Parkstone Electrics, Poole, 0202 746555. ESSEX Emprise,

Colchester, 0206865926. GLOUCESTERSHIRE

Computer Shack, Cheltenham, 0242 584343.

HERTFORDSHIRE Photo Acoustics, Watford,

0923 40698. Tek Systems, Stevenage, 0438 65385,

Chrisalid Systems and Software, Berlchamsted,

044 27 74569. KENTSwanley Electronics, SwarUey,

0322 6485 1. LANCASHIRE Harden Microsystems,

Blackpool, 0253 27590. Sound Service, Burnley,

0282 3848 1. Computercat, Leigh, 0942 605730. BEC

Computerworld (Liverpool) 05 1-708 7 100. LEICESTERSHIRE Kram

Electronics, Leicester, 0533 27556. LONDON City Microsystems,

EC2, 01 588 7272/4. Wason Microchip, N 18, 01 807 1757/2230. Premier

Publications, Anerley SE20, 01 659 7 13 1. NORTH EAST Briers Computer

Services, Middlesborough, 0642 242017. General Northern Microcomputers,

Har tlepo ol, 0783 863871. HCCS Associates, Gateshead, 0632821924.

NOTTINGHAMSHIRE Midland Microcomputers, Nottingham, 0602 298r 81.

Mansfield Computers, Mansfield, 0623 31202. East Midland Computer

Services, Arnold, 0602 267079. Electronic Servicing Co., Lenton,

0602 783938. NORFOLK Anglia Computer Centre, Norwich, 0603 29652.

Bennetts, Dereham, 0362 2488/9. OXFORDSHIRE Micro Business

Systems, Whitney, 0993 73 145. Pebbleglow Ltd. (Thame) 08442 1 5368.

SCOTLAND Esco Computing, Glasgow 041 427 5497. Edinburgh:

031 557 3937. Computer and Chips, St. Andrews, 0334 72569. Scotbyte

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04 1 22 1 8958. SHROPSHIRE Tarrant Electronics, Newport, 0952 8 14275.

SOUTH WEST Diskwise, Plymouth (0752) 267000. West Devon Electronics,

Yelverton, 0822853434. Bits and Bytes , Barnstaple, 0271 72789. SUFFOLK

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Thornton Heath, 01 689 1280. WALES Tryfan Computers, Bangor, 024852042

WEST MIDLANDS Allen TV Services. Stoke on Trent, 0782 6 16929.

WILTSHIRE Everyman Computers, Westbury, 0373 823764. B & D

Computing (Swindon), 0793 762449. YORKSHIRE Media 5 Ltd; Sowerby

Bridge 0422 33580. Advance TV Services, Bradford, 0274 585333.

Huddersfield Computer Centre, Huddersfield, 0484 20774. Comprite,

Bradford, 0274 668890. Supenor Systems Ltd., Sheffield, 0742 755005,

Photo Electrics, Sheffield, 0742 53865. Ebor Computer Services (York)

0904 791595. NORTHERN IRELAND Business Electronic Equipment,

Belfast, 0232 46 16 1 . Brittain Laboratories, Belfast 0232 28374.

Sole Importers:

efteciraiiics

Chesterfield Road, Matlock, Derbyshire DE4 5LE.
Telephone: 0629 4995. Telex: 377482 Lowlec G.

104 YOUR COMPUTER, JUNE 1982

**«L

RE MEMORY FOR MICfr6s !

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PAMPACKS

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CHEQUES AND P.O.'s TO:

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ALL PRICES INCLUDE VAT. AND POSTAGE

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A TRADEMARK OFSOLIDISK LTD.

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See it here, buy it now

AT YOUR LOCAL
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92A Upper Parliament St NG1 I 6LF Tefc 0602 40&76 Manchester 3yteshoo Compuicriand n Gateway House Piccadilly Statin Approach Tak06T 2364737 Glasgow Bytesnop Computertand Magnet
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*

A member of the Coman JLi Group of Companies